I've been floating around this forum for a little while, but never really registered because I never had anything to say. I recently did a speedrun (on a console) of Super Mario Bros. 2, and needless to say, I got intimate (it's not what you think, pervert) with most of the glitches/tricks in that game. I noticed that there were a few requests to explain some of the tricks for SMB2 on the Mario Tricks Page, so I'd thought I'd help out, or at least try. I hope I'm posting this in the right place.
Double Jump
The description that's up right now says that you can double jump off of enemies, which is true. My definition of it is that you can double jump off of anything that you can stand on that also has the potential to hurt you. This definition broadens the double jump to
most enemies (for example, the little plants that shoot fireballs are un-double-jump-able, because you can't stand on them), Birdo's eggs, and Clawglip's (I think that's his name) rocks (although I've never actually tried this one, it makes sense).
Mushroom Block Bouncing for Multiple Hits
I'm not sure what exactly this one means. To bounce a mushroom off a character's head, you just have to have it land on the character's head. I do this a couple times in
my no warps speedrun, like at the end of levels 3-1 and 3-2, I think. Most noticeably, you could probably do it against Fryguy in 4-3 for the most benefit.
Jumping Up Vines and Chains
This is by far the most annoying and frustrating trick (to do on a console). You can only perform the trick every 8 pixels on the ladder/chain/vine. I don't know if the 8 pixels is correct, but the point is that you can only do it at constant intervals on the ladder/chain/vine. My method was to press right/left and up at the same time, and then jump immediately after that. I imagine you guys know the exact method of doing it a lot better than I do. This is much easier to do with Luigi, for some reason. I think it's because he jumps the slowest (i.e. his acceleration after he jumps is much lower than the other characters, so his jumps are kind of "floaty"). See 5-2 in my run.
Running Across the Ceiling
This can be done for benefit in 7-2 and 3-2, and maybe in 5-3 (although it's definitely not faster to do on a console). But I'm sure that's common knowledge by now, it's just not mentioned.
Due to my crappy computer, I am unable to actually watch any of the runs from this site, so if I'm stating things that are obviously in the runs, I'm sorry. That's also why I referenced my run, instead of the tool-assisted ones.