Well, last time I went riding, I almost bit it because my rear wheel turned out to be loose when I was going off of a jump So after that, I decided to check my wheels each time I went out riding (which I should've done in the first place).

My question is, how tight is tight? It's not a quick-release. What would happen if I tightened it too much?

Use a wrench that fits the nut on the end of the axle and pushing hard at the end of the wrench should give about the right torque. That is why wrenches for large nuts have longer handles than wrenchews for small nuts.

Oh yea remind me of one time.

I tight my wheel with a real wrench real strong. When biking. Everything was dandy until I got a flat. I said to myself fine I had my patch kit with me and pump so let repair the flat. Try to unscrew the wheel with a multi-tool. the wrench I tight the wheel with is much longer than the mini multi-tool. There was no way I could get enough leverage to move the nut. It's solid. Fortunately after a while I got the clue to patch my tube without removing the wheel. Just remove the tire with wheel still on the bike upside down find the hole apply glue and patch put the tire back.

So morality of the story. Be sure you can remove the wheel in case you need to do it on the road with mini-multi-tools. You can also carry a large wrench with you but that don't fit in the saddlebag. Or you can just patch without removing the wheel but what if you have a major blown out. Not that it should happen normally if your tire are put on correctly but sometime freak accident happen.

EDIT:There is also the slow leak I can't see the hole and it's freaking raining. I just want to change the tube for the spare one I got. So be sure you can get the wheel off with whatever tool you carry with you.

That's why I always carry my air impact wrench and compressor... There's nothin' that puppy can't take off!