Street Fighter IV - Tips for an old SF2 fan

[manasecret]

I was perusing the PS3 section at Blockbuster, when my eyes fell upon Street Fighter IV. The perfect rent for me. It's a game I've been wanting to try since it came out, but a game I'll never buy.

But I haven't seriously played a Street Fighter game since SF2. I know all the moves for that game, and they're still here, but I notice there are tons of updates to make it interesting.

So, I need help.

1. How do you string combos together? Is it just a matter of knowing the right combinations?

2. How do you pull off the ultra move, the one that zooms in to your character? I've got the other lesser ultra moves down I think, just press two punches or kicks.

3. Any tips for Rufus specifically? He's a funny character, but I kind of got his moves down and found him fun to play.

4. How do I go about not sucking? I can't get past the 3rd round!!