I wait until they're available. I've never seen a reason to preorder a game. Even if they have something promotional. Unless it's really worth it, but I've never seen anything of worth to preorder a game. I mean you're paying full price no matter what. Unless you wait a long time, which is usually what I do as an alt to both of those.
I used to preorder things a lot, mainly because I wanted to be sure I got it as soon as it came out. I did this with Smash 3DS because I knew it'd be hard to find it for a while and didn't want to miss out on getting in on it during the first few weeks when online would be just insanely active, but that's the only thing I've preordered since five years ago now (preordered the original 3DS). I guess it's age bringing me more patience, but even most promotional things don't get me excited enough to get it set up. If I want it I'll get it, there's no need to be one of the first.
For me it really depends on the game and the DLC or items included in the pre-order bonus. I have been pre-ordering things less and less over the past year and a half because even series that I normally loved have been disappointing me (like Borderlands Pre-Sequel... glad I didn't buy the season pass for that crappy installment to one of my fave series otherwise). I admit I can give into the toyetic and cosmetic marketing sometimes. Like when Dragon Quest Heroes comes out I'll pre-order it for sure, but even if for some reason I was hesitant to do so, if it came with a blue slime keychain I'd pre-order it just for the keychain alone. With that being said, however, I've never bought the ones that cost 100+ dollars or anything - always the basic pre-orders.
I first pre-ordered Left 4 Dead 2 on Steam because I loved the first game and wanted to play it as soon as it came out. I ended up being really disappointed in it because I felt they lost the charm and atmosphere that made the first game so good (too much sunlight in L4D2). After that, I decided not to pre-order anything else.
However, I did pre-order Wind Waker HD so I could get the Ganondorf figurine. It was worth it.
Over here in the UK, I never pre order. Seriously, if a game isn't some sort of triple A big budget title advertised everywhere, it will pretty much never be sold out. Double so if it's on a Nintendo system.
I preorder occasionally, if it's something I really, really want, or has a nice preorder bonus. I mean, if I'm going to buy it day one anyway, I may as well preorder to get the bonus. We also have a Best Buy game club membership, so we get a discount on new games, so we tend to buy new. I also tend to preorder if it's coming out during a holiday season, or is bound to be really, really popular. The last games we preordered were Mario Kart 8 (There was literally a line out the door to pick it up when I got there at opening, and I got one of the last posters they had) and Super Smash Bros for 3DS and the bundle for the Wii U that came with the controller hookup thing.