when in doubt activate your king ecspecially in the opening to midgame transition. An active king is worth about three pawns so essentially if your king is in the corner of the board rather than actively placed in the centre you are playing a whole piece down. you can thank me later!
Help with a sticking point

p-wnattack, the king should only be activated in the ending, not the middlegame. In fact, bringing the king out in the opening is better because the middlegame is way more crowded than either the opening or the ending.

temuchan
It sounds like you know the lines but not what to do with them. Without seeing some examples of your play, I'll guess that the problem is that you get to a position that theory says is OK, your opponent plays something not in the books, you play a "solid" developing move, and your opponent crashes through for the point. Am I right?

If you think its based on not having a plan then pawn structures, annotated game collections, strategy books will help.
If it's a disadvantage big enough to lose the game it's probably based on your tactical ability and ignoring your opponents threats.
There's no easy way to improve.

p-wnattack, the king should only be activated in the ending, not the middlegame. In fact, bringing the king out in the opening is better because the middlegame is way more crowded than either the opening or the ending.
In that sichuation instead of bishop takes pawn, why not knight takes bishop?

I can't help but point out angrybirdstar's variation is incorrect and you should not worry about playing 5. Nc3, since the bishop on c5 is en prise after 6...d5.
The 'trap' he probably reffers to generally arises from:

angrybirdstar if you want to play a piece down in all your games go ahead. also it is never advisable to have your king in the centre in an endgame as by that time your king should've reached the other side

In that game, you lost by leaving pieces hanging; You have to remedy this before you start studying anything. Try to "blunder check" every move by thinking about your opponent's possible replies. This eventually becomes automatic with some more playing experience.

There are a few things to address here.
4.g3 Why? If you were going to fianchetto, then what was the point of 3.Bc4? 4.Nf3 was better; if black plays Nf6 you need to watch for the old idea of ....Nxe4; Nxe4, d5 for black--so 4.Nf3, Nf6; 5.Bb3 and you're still playing chess.
5.Bb5+ Again, why? The B was fine were it was; remember that thing called "developement"? Either 5.d3 (stregnthening the center) or 5.d4 (to open the position against an opponent who is just pushing pawns) seem better; even Nf3 is OK, I suppose. Your move forces black to move a piece when he was happy moving pawns. If the LSB moves anywhere, it should be to g2, but Bf1 here is ridiculous.
6.a4 What's the point? You already own b5. Again, developement. Get your pieces out.
8.f3 More pawn moves. 8.Bg5 to take the N/f6 to mess up black's pawns and give the N/c3 some access to d5 seems more to the point.
10.Ba7 This move is bad. You toss away a B for nothing. I'm just asking here, did you not see Bxc4? He just gives you a pawn.
Alright, this is just one example, so I'll try to keep it broad, but focused. You play your first few moves with general rules in mind, but then seem to drift, you have no "grip" on the position. You are just playing moves, not battling your opponent's ideas. If you find yourself treading water instead of swimming to the finish, try simpler set-ups like the Catalan, where you have a similar set of moves to play against almost all black replys. But you'll do a lot better for yourself if you concentrate more on learning the middlegame and tactics than you would the openings.
Hanging pieces, it is very typical for beginners. Check if your opponent attacks any of your pieces, and protect them. Also, if you place your piece somewhere (but generally you should be more careful when you put a piece into your opponents territory, since that is controlled by your opponents army) check if you opponent can capture it.
You can't play chess ignoring your opponent's threats.
And just to help you in the opening stage.
- You should develop your pieces
- You should control the center. In the opening, a pawn move is good, if it helps you to develop a piece, or helps to control the center. Otherwise it is bad.
Then castle.
Connect your rooks by moving the queen. Your development is ready if you have your rooks connected.

That's the issue I've been running in to, it seems like every book/article I read is designed for people past the point of making the basic mistakes I make. So the solution is to keep playing until I am able to make sure my losses are due to being outplayed tactically as opposed to mistakes like hanging pieces and then look for texts?
Edit: This should have posted after your post FancyKnight...

At this point I recommend that you get some games in. Any chess book is going to be meaningless if you're hanging pieces.

Keep playing. The only good advice I can give is (1) Don't hang pieces and (2) develop in the opening (first 10 tips suffice for a good game). That's all you need for now. (These two pieces of advice can get you shockingly high if followed well.)

Dashkee94:
Yeah, looking at the game again I didn't see 10.Bxc4, seems really obvious to me post-game. My thought process here was that I did not want to give up my bishop's "position" as being deep in enemy territory, which is why I played 6.a4, to strengthen my bishop's hold in b5. This is a thinking flaw on my part - the assumption that deeper=better. Your recommendation here would be to not have put my bishop on b5 in the first place?
You suggested 8.Bg5 to pressure the knight, if I were black I would reply with ...h6. I was always told not to move a piece early that will need to be moved backward, out of curiosity what is the reasoning behind 8.Bg5? Would ...h6 be a bad response for black?
Treading water instead of swimming is a great analogy, the only direction I have is take pieces and try to checkmate. I know where I need to go but I swim in circles trying to get there.
I tend to get stuck after the opening during the transition to mid game. I tend to make a bad move around move #8 or #10, one that puts me at a disadvantage large enough to eventually lose me the game. I think my problem is not knowing what to do next (aggresively) so I just keep developing pieces until I fall into a trap and end up forced into a bad trade. Any tips for this stage of the game?