5: In the beginning, the fourth line is big, the third line is nearly as big (oriented more towards safe territory), the second line is small (not a lot of territory under there) and the first line should be avoided at all costs.

13: This is a good idea: you approach the corner, he doesn't do anything to protect the corner, so you invade. The problem is that the best time to do this was a move earlier (:w11:), not immediately after he plays o17.

23: This is okay. You have a lot of cutting points and you have to sit down, relax, and try decide which ones are most important to defend. I would prefer r18 to q14, but the keep think is to carefully think it over and look at what move your opponent will make next.

25: This is a little early. When you invade the corner, black gets a thick wall facing the side. If the board is empty, his wall is worth more than your corner territory.

27: This is bad because it invites black to slice your two stones in half with d17. Now anything you do to strengthen one stone, weakens the other. You can look at josekipedia to get some ideas for how to proceed when B ignores the 3-3 invasion (look at the sequences where black plays at 3-3 in an empty corner, then white plays 4-4).

28: A bad mistake: d17 is great for black.

29: Good, now you're both cut in two.

43: G16 is fine for you. Whether black defends the top or the center, he's digging his own grave.

57: Good job on not saving that meaningless stone at c15. But what good is this stone doing? Did you read out a sequence where it becomes helpful?

59&61: B12, I think. Try to read out how he'll escape.

69: What do you get by saving this stone?

70-80: You seem to be convinced that unless these black stones die, you'll lose the game. In fact, if you could safely wall him in and then turn your attention to the center, you'd be in a great position.

89: Why not pass?

92: This is a great example of a small, gote, meaningless capture. That would be a fine for move 192, but on move 92 it's way to early; there's a whole corner that hasn't even been approached yet! Maybe black should have thought about it for more than 3 seconds.

93: Not sure what your goal was here.

95: This is a fine move so long as your goal is to start a messy fight.

96: This is a bad mistake: Black has a broken shape the white can slice through.

97: Good.

101: J15 instead. That seals in the black group. Now black can cut through break white's shape instead.

102: No, black has to slice through at J15.

121: This is the right move, but be aware that at any time now, B can capture B16 by playing B17. That's worth about 7 points.

125: You're begging black, "Please, please strengthen your position? Pretty please?" You want to cut through at L15 or J13 if a local move is important. I think the lower left is biggest now, though.

143: White is strong enough in this area to play L11 instead of capturing directly. (In general, capturing directly is the right move, but first, capturing four stones is rather small: second, this position is extremely strong, so the risks (what we call "bad aji") are miniscule.)

146, 152, 153: Bizarre moves.

151: It's good that you saw that black can capture by playing here. Ideally, you would have seen that before you play T16, and would have known that it wasn't worth it (since you then have to make the safety move). Also, are you sure these three stones are bigger than the seven stones at B16?

155: You're making this weak, hard - to -defend group of stones heavier, and black doesn't even really need to respond.

161, 163: This is called a ladder When your opponent puts you in atari, try to read ahead and see what happens if you pull out of it.

165, 167: Now, really, what did you think would happen?

After this point invading the lower left corner is pretty big.