I'll layout my different campsite for my trip last year.
1st night: AT trailhead 5 miles east of Bennington, VT. I camped out right beside the privy under part of the overhang. It did, and was suppose to rain overnight.
2nd night: A strange location. Right beside US20 in NY. I'm not sure who owned the property as it was a pulloff not really a driveway. It had limbs and tree stumps around the area the top of the pulloff. When I looked at it later on Google Earth there wasn't any house within at least 1/2 mile of the pulloff. It was in farm country but the place looked very strange. I still wander if it might be state owned land.
3rd night: Behind a church. Didn't ask as there was no one around.
4th night: Behind a truck stop.
5th night: At the entrance to a gravel pit. This happened to be a Saturday night so I knew I didn't have to worry about anyone coming in early in the morning and seeing me. Turns out I missed the No Trespassing sign as I went in. I saw the sign as I walked out in the morning.
All of these sites were within easy earshot of the highway. I was generally only 50-100 feet max off the highway where I camped each night for the first leg of the trip.
After spending a week at my mom's place I continued on west and headed off for St. Louis. This is when things started to change and my idea of potential campsites really started to change.
6th night: Across the street from Wal-Mart in Logansport, IN. As I got into town I started looking for spots. I saw a vacant shopping store and decided to check out behind it. Turned out not usable due to rental/condo area right behind that. Didn't like the feel of it. Toward the far end of the parking lot was a storage unit facility. I rode down there and continued looking. It was getting late. Nothing. I saw a path that led into the trees. I walked back the path and it came out into what appeared to a auto dealers parking lot. When looking at the entrances the next morning I saw it was part of the auto dealers lot. It had several vehicles sitting in the parking lot and one of them happened to be a Budget rental truck sitting right by the overhead light. I saw it and loved it instantly. It was remote enough I decided I to give it a shot. When I woke up in the AM and went to head out to find food for the day I found I was right across the street from Wal-Mart.
7th night: Chickened out thanks to getting into town after dark and drenching wet...I went for the hotel room.
8th night: Questioned how far I would make before running out of daylight and I saw I should be able to make into Auburn, IL. I did and their was a ballpark on the east side of town I saw on Google Earth(GE) that looked like it should be a nice spot. I got there and found it better than I expected. Probably the second best night of the trip.
9th night: Saw a few potential sights on GE but when trying to find them in person everything was running dry. Nothing I really liked the look of in person. I hopped back online after getting into town and saw potential cemetery. I waited until after dark and as I pulled up by the cemetery I had the clean/no traffic coming down the road and no signs saying the cemetery was closed after dark...I went in and spent the night.
10th night: The most interesting/balsy I would have to say of the entire trip. Got into town late, not much before sunset. I saw a couple of vacant buildings that I was thinking of investigating further after it got dark. I went into McDonalds, right beside the interstate and grabbed supper. I couldn't get online so I was pretty much winging it. As I walked out of the McDonalds I was ready to collapse right where I was. I wasn't looking forward to finding a campsite. I had ridden my second 130+ mile day in a row. I looked and saw the semis parked behind the McDonalds and 'beside' as well. It was pretty obvious this was a bit of a truck stop. Like I said the on ramp for the interstate was 100 feet behind the end of the McDonalds parking lot. There was at least on hotel right in the same group of buildings. I looked and saw right behind the gas station was a spot about 4-5 feet wide. 200 yards behind it was a Wal-Mart. The two spots were separated by a corn field. I looked at it and I knew I was crazy. I took it and spent the night there.
11th night: Another trailhead I had seen a few days in advanced on GE.
After another week or so off at my moms place I headed on home.
12th night: Best night of the trip. I found online a nice city park, less than an hours ride from downtown Columbus, OH. I didn't realize the spot was going to end up being as nice as it was. It wasn't far from the US40. I missed the main turn in off the highway so I instead ended up getting in at the bike trail crossing down a side road with the same name as the park.
13th night: I wasn't carrying the best camping equipment and I knew it wouldn't be comfortable much below 50 degrees. The forecast was calling for mid 40s. I bailed and went for a hotel room so I wouldn't have to worry about the crummy equipment.
14th night: As I pulled into town I searched up and down business row. I found the local Wal-Mart had box cars sitting behind the building that were used for extra/overflow storage. Their wasn't much room there on the opposite side of the guardrail but it was enough thanks to having a free standing tent that I could set up camp right behind the box cars. Like had become the norm, I waited until after dark and snuck in and I knew if they wanted to complain I could complain as well. They let people camp out in the parking lot with RVs so why can't I sleep in their parking lot as well.
15th night: Goofed getting into town. I missed my plan turn and had to head back out to the business district using an alternate route. I saw the Lowe's store way up on a hill. I like the look of it. I was still going to try to find my original spot which I never did find. GE made it look like their a was road behind the Wal-Mart that went up to potentially a water tower. It looked like that at least. The entrance to the road looked quite nice. I never did find the road. Instead I went back and camped out up on the hill behind one of the delivery trucks at Lowe's. There was some town owned property up on the hill as well that had a water tower on it. It wasn't the same spot as I wasn't looking at originally though. One of the workers/drivers tried briefly to make some noise in the morning to get me to 'stir' but I didn't.
16th night: Definitely not the intended location by a WIDE margin. Got into town. Looking on GE I saw a nice ball park on the east side of town. I was planning for it. As I finishing off an email it hit me. I had the hot flash followed by the cold sweat. I knew I was in trouble. It was after 10PM already. I knew I was screwed. I didn't know how long it was going to be but I knew I was coming down the stomach flu. As I had initially arrived in town I stopped by the Sheetz gas station just two doors down from McDonalds. I grabbed a sub in there and ate it before heading off to McDonalds to get online. At the same time I saw what looked like a potential campsite right beside the gas station, on the gas station property. I also semi liked the looks of the property right behind the auto service shop between Sheetz and McDonalds. When the stomach flu hit I knew I wanted, for safety sake, to be around someplace that was open 24 hours...the Sheetz gas station. I finally said the heck with and didn't care if I got visited by the police. I knew if stayed at the gas station I would more than likely get paid a visit. I was going to be camping out right beside the back/side door to the gas station. Anytime an employee came out I was nailed. It took until 4AM before I heard the door open and 15 minutes later I saw the headlights and knew it was the cops. They had me move over to the auto service shop lot and didn't say anything more. This was a college town. I did get bothered by some of the college kids. It was a Thursday evening. I didn't know about Thursday evening/college towns until this experience.
17th night: Rode 24 miles into the next bigger town and spent the night in a hotel. Finally kept supper down this night. Hadn't kept anything down until supper.
18th night: Was thinking of going for a motel after riding 146 miles for the day. First one didn't take money after 9PM and the second one was smoking only and $80+. I said the heck with and I had seen Salvation Army had a big facility in town. I figured they would let me camp out on their property. This was a small housing unit property, the SA store was closer in toward town. I got there and walked inside and asked if I could camp out beside one of the buildings. They said NO. I walked out starting to question what my next move might be as it was after 10PM. A guy followed me out the door and yelled at me and I turned around and he ended up telling me right beside the SA housing unit was a walking path with a stream running beside it. He said if I didn't set up my tent I should be able to get away with spending the night there. I walked down and took a look. I walked back toward the trees up against the SA property and set up the tent and spent the night. I knew by setting up camp where I did it would make it even less likely that I would be spotted.
19th night: Another cold night forecasted so I bailed for a motel room again.
20th and final night: After not following my planned route for the day, missed a turn that turned into missing quite a few other turns, I ended up back in Bennington, VT. I was going to grab a motel room for the final night but they wouldn't take a check. I left and headed back into town. I wasn't going to ride out to the trailhead. Instead I ended up finding what looked like a potential spot just down the road from McDonalds in town. It was right beside one of the shopping strips. I rode down there and found wetlands. Nope. I looked a little more and saw some dumpsters sitting right up next to the back door of the Shermin-Williams store. I knew I was going to be up and on the rode VERY early in the AM. I was trying to outrun the incoming rain. Other than night 7 it had been dry the entire trip. I wasn't worried about any employee catching me as I was going to be on the road before 6AM. I camped out 4-5 feet from the backdoor of the Shermin-Williams.
There are many places where you can crash for the night if you are willing to look around. Go with your gut feeling of worth or not the place feels safe. In major metropolitan areas I probably wouldn't try camping out in town. In smaller, under 10,000 population I probably would without batting an eye at it. The smaller the town the more likely I would do it. Learn to look for places and you will find them. If you never seek you'll never find.