Since everyone's asking about Sq1 now I just copy paste this
The most important part is probably cubeshape. Learn scallop-kite ("advanced cubeshape"), and use this list. It's like F2L; don't try learning all of them, but check the list often to see if there's anything you haven't tried.
Learn some EO and CP from here. I would suggest this order:
* One-one (DG's alg is silly)
* M2 (using this with one-one gives a decent solution for L-I, I-L and three-three)
* Double M2 (just the previous alg twice)
* L-L (short alg and very similar to the EP alg, and you can't solve it with M2+one-one)
* L-I (very similar to one-one)
* Three-three (also similar to one-one)
* I-L (quite unique alg so will be harder to learn)
For CP:
* Double J (short alg and is very useful)
* Double N (even shorter alg but rarest case)
* N-J (very simple alg, just R2 U' R2 U R2 U' R2 U R2)
* J-N (mirror of previous alg)
* Bottom J and top J
* Bottom N and top N
And for EP:
M2 U2 M2 is very useful. With that and the other two algs, just work on solving cases efficiently.
The most important part is probably cubeshape. Learn scallop-kite ("advanced cubeshape"), and use this list. It's like F2L; don't try learning all of them, but check the list often to see if there's anything you haven't tried.