An aspect of importance (and one which a lot of players overlook and/or have little knowledge of) is where you are sat at the table for each hand. Your position dictates your turn to act - to bet, raise or fold. When it's your turn to be the virtual dealer you are known as being on the button. This can be very powerful.
When you are in an early table position you have to act first or before the vast majority of players. This can be very difficult as at this point you have no idea what cards others could be holding. So, if you decide to enter a hand from early table position be sure it is a hand you really want to play. Think what you would do if a player acting after you raises the pot. Is your hand good enough to match that raise? For example you're in early position, you look down at your starting cards and you have JT. Not bad, but not great. You call. Another player throws in a big raise. Action comes around to you again - what could the raiser have, is your JT up to the job. Is it worth calling that big raise to see the flop. Play the strongest starting hands from early position and be prepared to call a raise if you do.
When you are in a middle table position still only play very strong starting hands (say group 1, group 2) because there are still a good number of players to follow you who may raise. If a player from early position has already raised, I'd get out now with anything other than a group 1 hand. Middle position is still tough to play from so select those starting hands carefully.
When you are sat in late position (on the button or next to the button) you have the advantage of seeing what everybody else has done and know that only the small and big blinds have to act after you and they have already been forced to put chips in the pot. Being in late position is an advantage. Say nobody had raised the pot so when play gets around to you - a few have folded, the remainder have just called. Nobody has shown that they may have a strong hand by raising the pot. If you have a reasonable hand here, throwing out a small raise at this point even with a marginal starting hand could take down the pot there and then as you are showing "strength." It also puts pressure on the players in the blinds as they now have to decide whether or not to put even more chips in to the pot over and above their "forced" bets.
In general - use table positioning to your advantage and be aware of it. Play only the best cards from early position. Look for opportunities to raise from late position if you think other players are weak and/or to attack the blinds. Master table positioning and you can take down more pots.