1st off, no matter what you, there will always be somescum that will or try to lift your bike. These tips will make it much more harder for a person to steal your bike(s). Remember, the longer a thief has to hack to get to a bike, there is a good chance they will get caught or there will be witnesses.
1st step-sacrifice the easyness of quick release levers, and get a pair of bolt ons. A thief doesn't carry a allenwrench, it takes too much time.
2nd step-When locking your bike on a post, make sure the post is thick, and it is directly mounted into the ground, no separate parts that can be unbolted.
3rd-When leaving your bike locked, outside for more than a few minutes, take of anything that is removeable. A thief won't want just a frame, they go after the full ten yards.
4th-If the place you're going to has a front window, with one of these posts, lock it to that post, and at various times, keep an eye on your bike.
5th If you go to a friend's place, ask them if you can bring your bike inside, if not ask them if you can put it inside their garage or shed, and have the garage door closed. If a thief breaks in, they will be stupid, because, they would get nailed for a much more serious offense, breaking and entering.
6-If you ever have to go to a shady section, or a section you're not familiar with, have a friend or family member drive you there. It's not worth the chance in this case to have your bike potentially stolen.
7-When locking your bike, use more than 1 bike lock. a chain/cable to lock onto pole or bike rack, and a U lock to lock the wheels and frame together, no movement is your friend in this case.
8-Register your bike, with town, state, and with a national database, in the case if it is stolen, there is a better chance to recover bike.(Hopefully the previous steps will have prevented this.)
9-Inside the handle bars or seat tube, put a laminated piece of paper with your, name, bike's serial number, date bike was purchased, where it was purchased. In the case if the person who was found with it gets questioned and denies that he/she stole it/bought it from the person who stole it. Tell the cops in the case if it was stolen in your report where this piece of paper is, if they find a person with this bike that matches your description, they can check that area, and if that piece of paper is there, you have your theif, or you have a lead.(Hopefully this won't happen either.)
Hope these measures will, help.