My advice would be (in no particular order):
1 - Exercise patience, be more selective as it takes more experience to play mediocre hands profitably.
2 - Don't assume everyone is bluffing. Most players never bluff. Only a few do, and they usually can't help themselves from it.
3 - Racially profile your opponents. Of course, I'm not advocating that you judge anyone based on race, as I'm not a bigot, but do understand that different cultures have different approaches to gambling. This will help you more than you might think. It will also help you to understand how your opponents think. If you don't know how to do this, talk strategy with your poker friends from different cultural upbringings.
4 - Pay attention to board texture. If you don't know what that is, then study it until you do
5 - Did I mention board texture? Ya... study it again
6 - Exercise bankroll management. Don't know where to start? Head to two-plus-two and study it...
7 - Young online poker pros are MUCH better than most TV pros (trust me, I've played with almost all of them). If you want to improve your game, find out who is worth studying, and read everything they have to share. Then, read it again. (two-plus-two is a good place to start)
8 - Watch instructional videos online (shameless plug for my videos on pokerstrategy.com if you want to work on your mixed games)
9 - Review EVERY SESSION you play online. Find your mistakes and track them. Attempt to minimize mistakes. Watch them go down over time. Celebrate when they do.
10 - Move up in stakes when your bankroll supports the decision, assuming it comes from poker winnings that is. You can create bad habits if you don't.
11 - Learn to identify good, winning players. If you're at a table where most/all of the players are better than you, it's time to pick up your chips. This is not the time to learn.
12 - Figure out which games you're good at, and play those (MTTs, STTs, LHE, NLHE, PLO, O8, Stud, etc).
... I gotta run, but that's a start. Good luck!