Rafa vs Psk31: Let's have a look
http://files.gokgs.com/games/2010/10/2/Camarao-psk31.sgf
6: This moves tries to pressure the approach stone and enclose territory in the corner, but I feel like it doesn't do either as well as I'd like. D5 lets you threaten to pincer, but also works towards building a safer framework. C5 wouldn't be bad, but D5 lets you lean on black's stone a little, which you seem to want.
13: I saw a go problem similar to this, telling you to defend your corner. The correct move was R5, because it defended the corner a bit while also threatening the nearby two-space extension group. After R5, you could either take O3 to button up those corner points, or you could do something in the top right.
14: I prefer threatening back, at Q6, or even playing solidly at Q7. Your move is the correct one to play when you want to lightly reduce territory, sacrificing stones when necessary. However, your straits aren't dire enough yet for you to need to play that kind of sabaki, I don't think.
15: Not bad, but do remember: this move doesn't actually seal up that corner territory. Later, if you want all of those points, you'll need something... maybe P3 or Q3.
16: Taking the corner is pretty big here, though I like the thought of threatening those two stones below.
21: Letting your opponent capture here is big. R17 is more useful for the corner, or O15 helps more if you want the top side.
24: R18 takes the corner, stabilizes your group, and undercuts black's three stones. That said, you have a good idea behind this move, as it extends from your corner and denies an extension to black's stones. If you're going to play it, though, play it on the third line. The fourth line lets black threaten the slide when he takes M17.
25: Playing on the third line here threatens to slide under, and better secures your eyespace. Otherwise, white can play at M17 here, to attach and connect safely.
30: Unless you can read to conclusion a definitively better result, simple is better. Just connect against the peep.
32: Black's connecting threatened to cut at the peep. Now you need to go back and defend it again or have it cut off.
33: Similarly, you can cut white off.
37: Another of those ever-popular rules of thumb is, don't create weak groups near your other weak groups. Otherwise one or both will get attacked painfully.
53: Choose between this move (it's a reasonable option), G8 to save the three stones, and C3 to try to live in the corner. Your move is fine, but these are other options.
61-91: You both used some good fighting moves in here. There were mistakes, but all in all, good instincts/reading.
131: S5 is also safe, but it also threatens, making it sente at least. Also, it's still pretty hard for white to live.
137: You're connecting something that's already safe. N4 is HUGE, because if you don't block, white can reduce you strongly.
You both played a good game. You definitely have a lot of the right ideas, a lot of it is just finding the right specific move in the area you know to play. The two biggest things to work on are these:
First, whenever you make a new group, consider how it will affect your other groups. If there is a chance it might get weak and have to run, such as when you pincer, make sure that you don't have any other groups around that will be weakened as a result. If your other groups are safe, then you're all set. If your groups are not yet safe enough for that, consider defending them first to prepare for the attack.
Second, any time you want to be aggressive, consider this: if your opponent were to get sente from this fight, could he do something nasty to you? If so, you are being too aggressive.
Let me know if you have any questions!
