There's not necessarily a rule for when you should be doing something. For instance, if you're masturbating at 13, great. If not, that doesn't mean there's a problem. You don't need to do it. For other things, it will be a matter of morals. Is it okay to have sex at 13 (if both people consent)? That's an ethical decision you'll have to make.
As for what to look out for, there's nothing in particular. Puberty happens a little differently for everyone.
You should make sure you post in at least TWO non-P101 threads for each post you make in P101 to help you maintain perspective on what is important and what is not important. I stick to a 4 to 1 rule myself but 2 to 1 is a good start.
Because anything puberty-related can happen at any time throughout the duration of puberty, you really shouldn't be looking for anything. You should be looking for everything because it could happen tomorrow or in ten years.