First of all, and more important than anything else by far: if you are a beginner, don't worry about positional stuff (yet) ! Learning chess theory (positional chess) will teach you how to form a correct plan, but that skill is completely useless if you can't execute it skillfully - a poor planner with good tactics will beat a great planner with poor tactics, every time.
Thus, if you are below 1800 USCF rating, or you don't know what your rating is, I would suggest focusing solely on tactics, and ignoring everything I'm about to say until you've improved more.
So, you're over 1800, you're satisfied with your tactics, but too often you end up with positions like the one shown above, and have no clue what to do next. Now what?
Now you learn about the various imbalances in the game, how they work together, and how to take advantage of them. This also means learning about endgames, as having the favorable imbalances will usually turn into having a favorable endgame. These are book-length topics, far too large to explain in one post; fortunately, there are lots of good books out there.
The best books for learning the basics of both of these things are both written by the same person: Jeremy Silman. For chess theory, I would recommend How to Reassess Your Chess, 4th Edition (make sure you get the 4th edition - it is vastly different from the earlier editions). For endgames, check out Silman's Complete Endgame Course. Both are very easy to read, and are geared towards players between 1400 and 2100 levels.
Now that you're comfortable with tactics, and have read the books I recommended above (right? :P), and know all about the various imbalances in different positions, let's take a look at your position in-particular. What are the imbalances in your position?
- Pawn structure: The first thing to note is that it's a closed center - this means, unless you can rip open the center, play will likely occur on the flanks (sides) of the board.
- Control of important squares: White has clear control of
d5, while black has
d4 - these are excellent outposts for knights. However, white also temporarily has
f5 available for his knights (temporary, because they could easily be pushed away by pawns), while black does not even have the option of knight-to-
f4, as they are guarded. Both
d4 knights would threaten
Nc7+ (forking king and rook).
g3 has white committed to the push
f4, but has left white with a glaring weakness at
h3 - he should work quickly, or black will take advantage of it.
- Development: Black is actually hindered in development, because he made the (poor) choice to bring his queen out in front of the rest of his troops. This will likely come back to bite him, as white can push the queen around with his pieces, forcing black to waste time moving his queen, while white happily develops his own pieces in the process.
- Bishops: White's light bishop is his poor bishop (ie. most of his pawns are on light squares), while black's dark-bishop is his poor one - so white would like to trade light-bishops, while black would like to trade dark-bishops.
- King safety: Black hasn't castled yet, but still has the choice of either king- or queen-side castling. White already castled, but moved his
g-pawn, leaving a weakness on
So, what does all this mean in the end? Here is my interpretation of the above (note that I could be completely wrong - I am a strong player, but no grandmaster):
Either player could still (hypothetically) have good play on either flank. White could play the queenside by playing for a
b4 push, or the kingside by
f4. As white, I would prefer the queen-side play, simply because opening the kingside with black's queen and both bishops right there is ominous.
Black could play the queenside by
b5, or the kingside by playing for
hxg3, bringing the rook into the attack as well. As black, I would prefer the kingside right now, knowing that white will probably try to play the queen-side (or lose the fight if he tries to go kingside, due to black's better development, and white's king being there).
Unfortunately, due to black's poorly-placed queen, white has an immediate threat:
1. Nd5!, forking the queen and
c7. Then after
1.. Bxd5 2. cxd5 Nb8 (to answer white's next move)
3. Qa4+ Nd7 4. b4 White is quite obviously winning: he has the double bishops, the initiative, better development, and his attack on the queenside if moving along while black's kingside attack hasn't even started.
It's black's move, but he doesn't have a good response to this threat; his best move appears (to me) to be
1.. O-O-O, but then after
2. Nd5! Qg6? 3. Nh4! Bxh4 4. Bh5 the queen is lost; thus after
1.. O-O-O 2. Nd5, black's only response is
2.. Bxd5, leading to a position similar to above, favorable for white.
So white has a way to force a highly favorable position, but the game is still not won. As black, don't give up - you still have your kingside attack! Make sure to deal with white's queenside-threats, but don't allow yourself to be lulled into playing defensively!
Note that this analysis would be very different if black's queen were still on d8 - in that case, I would probably say black has a slight-edge, since he can still choose to castle on the kingside, his strong side, and attacks in otherwise-even positions tend be slightly stronger when they are on the side the enemy king has castled. So the real answer is, stick to your first-principles; don't move the queen out too early! :P