What to look for when making a plan?

I am having trouble finding a concrete plan in my games. What should I look for when I am trying to make a plan?

look for weaknesses you can exploit and force matters; that's tactics. the strategy is the long term consequences. Force your opponent to make concessions; material, space, positional, time, safety of king.

Generally the pawns dictate which area of the board it makes sense to seek an advantage, queenside, center, or kingside.  Usually it's the area where you have more space (thus the rule of thumb to attack where you pawn chain "points") or the area where you have more active pieces.  And usually in that area you aim for a pawn break.  If there's no pawn break then you can try just piece play (targeting a pawn weakness, infiltration, targeting the king).

Generally if you can't do these things then your position is passive and you're stuck defending, meaning something went wrong at an earlier stage.

-------

The process isn't easy though.  While executing your strategy not only do you have to avoid losing to tactics, but your pieces need to efficiently go to active squares, usually where they're protected, can't be chased away, coordinate with each other, and not block each other. 

First a player should work on very consistently not losing pieces and pawns to tactics, and when their opponent offers free pieces and pawns via tactics, to very consistently win them.  Many strategic maneuvers are made possible because both players see and avoid short term tactical pitfalls.  As far as strategy, in the beginning it's focusing on trying to give each of your pieces a useful job or increase mobility.  Many beginners learn to develop all their pieces, but after 10-15 moves they don't carry that philosophy into their middlegame, and will ignore their inactive pieces until they've traded off all their active pieces.  As one saying goes "an amateur plays with their best pieces when a master looks for their worst pieces"

Examples of making a piece active (other than moving them all off the back rank except your rooks and castled king) are bishops on long diagonals, bishops outside the pawn chain (for bishops the same color as your pawn chain) rooks on open or half-open files, and knights on outposts.  When in doubt, centralization is good, and moving a piece out of the center to the edge is bad.

I'd say, as above:

(1) Analyze the position, especially for weaknesses or mistakes, which, if any exist, will determine the correct plan.

(2) It depends on the opening. In the Najdorf Sicilian, for example, Black attacks queenside while White attacks kingside. In some openings the attacking flanks could be reversed, or nonexistent. Part of learning an opening is learning what to do in general after one player departs from the book moves.

For very general advice across all openings, here is some book advice:

----------

(p. 187)
Rules for middlegame attacking

A few generalizations can be made about the middlegame, as long as you
understand that every position is unique and that exceptions are lurking out
there like fleas just waiting to bit you in the ankle. The following are a few of
the generalizations.

Attack if you control the center
If you attack without controlling the center, you are exposed to a counter-attack
in the center and your forces may be split.

Meet a flank attack with action in the center
If your opponent attacks on either side of the board, your attack in the center
divides your opponent's forces and conquers them.

Be prepared to develop quickly to any area
Your rapid deployment of pieces to one area of the board may be decisive if
your opponent can't respond as rapidly.

Place queens in front of bishops and behind rooks during an attack
The bishop is not powerful enough to lead an attack, and the queen is too
powerful to risk, if the rook can do the dirty work in her place.

(p. 188)
Don't place your knights on the sides of the board
Knights control too few squares from the side of the board, and their attacking
power is severely reduced.

Attack in the case of opposite-colored bishops
Because opposite-colored bishops can't be exchanged for one another or
control the same squares, the attacker has what sometimes amounts to an
extra piece.

Exchange pieces to help your defense
You have fewer pieces to trip over one another if you exchange pieces, and the
attacker has fewer pieces to threaten you with.

Put the rooks on open files (and the same file)
Putting the rooks on an open file and then on the same file (which is called
doubling) whenever possible is helpful. Other pieces can zigzag their way into
enemy territory. The rook requires an open file in order to successfully invade.
Two rooks acting together can control more territory than one alone.

Put rooks on the seventh rank
Rooks on the seventh rank can usually attack opponent's [sic] pawns that have
remained on their original squares; sometimese the rooks can trap the
opponent's king to the back rank.

Advance pawns to open lines
The opening is the time to develop your pieces [sic] not to waste time with excessive
pawn moves. Conversely, in the middlegame the pieces are already developed;
it may then be appropriate to make additional pawn moves in order to open
lines or create weaknesses in your opponents [sic] position.

Always guard against a counter-attack
Never leave your king exposed! Chess players very often spoil promising
positions in their zeal to attack because they forget to first take a few small
precautions. Sometimes it's proper to make a move or two to safeguard your
own king's position and only then resume your more aggressive pursuits.

Use knights in closed positions and bishops in open ones
Bishops need open lines in order to profit from their long-range attacking
abilities. Knights are more effective in skirmishes at close quarters, and closed
positions are more apt to produce that sort of skirmish.

(p. 189)
Attack where you control more space
If you attack when you control more space, you have more room to maneu-
ver your pieces, an your opponent has less. You then have more squares to
choose from when posting your pieces and you may be able to swiftly shift your
pieces from one point of attack to another while the defender struggles to meet
your threats.

Eade, James. 1996. Chess For Dummies. Foster City, CA: IDG Books Worldwide, Inc.

Before starting a middlegame plan, you need to complete the opening principles:

Control the center

Develop your minor pieces toward the center

Castle

Connect your rooks.

Now youre in the middlegame, and this is where you start to come up with a middlegame plan.  A simple middlegame plan is to scan your opponents 5th and 6th ranks (3rd and 4th if your black) looking for weak squares, and or weak pawns.  Weak squares or pawns are squares/pawns that cannot be defended by another pawn.  Weak squares/pawns closer to the center are ideal.  Knights make excellent occupiers of weak squares.  Rooks doubled on open files should attack weak pawns. 

Principle of attack.

Attack when you can – How can I move my pieces to my opponents side of the board, and take, or attack something?

Second step of your thinking process – If none of your opponents pieces are on your side of the board.

3 Principles for Improving your Position:

1. Principle of maximum activity.

move pieces before pawns – pieces have more scope, and range. Improving piece position, improves piece activity

go as forward as possible

occupy the center

2. Principle of the center.

keep your pieces in the center

3. Principle of the least active piece.

After deciding what piece to move. You then apply the Principle of the Center, and the Principle of Maximum Activity, in order to decide on where to place the piece.

Third step of your thinking process – Only if your opponent has pieces on your side of the board.

Principle for Decreasing your opponents activity:

1. Principle of neutralization of your opponents most active piece.

Removing your opponents pieces from your side of the board

What about Tactics, and Calculation?

Tactics are usually Forcing moves on your opponents side of the board

1. All you need to think about is:

How can I move my pieces to my opponents side of the board, and take, or attack something?

2. Find a few candidate moves

You need to consider 2 factors – the material on the board, and piece activity.

Attack attack and attack

What you should look for are weak pawn, squares and pieces

Yeah, honestly I was just thinking of closed positions :p  To me dynamic / open positions don't really have a "plan" so to speak, it's just be concrete and use your initiative or development before it's gone.  I guess that's unfair/misleading to the OP though.

Make a checklist of Kotov's list of advantages:

Permanent advantages:

1. Material
2. More central pawns
3. Passed pawns
4. Weak opponent squares
5. Better pawn structure
6. Better minor pieces for the situation (e.g., a bishop without a counterpart whereas his bishop is bad)

Temporary advantages:

1. Vulnerable enemy pieces
2. Superior coordination
3. Control of the center
4. Controlling a rank, file, or diagonal
5. Space advantage

Then create a plan based off this, then formulate candidate moves.  Choose the move you determined would maximize your advantage while minimizing theirs, and force them to make concessions.  Superior coordination and controlling a line for example can be converted into a more permanent advantage, such as superior pawn structure or even material. 

"Attack attack and attack"

I strongly disagree.  You can't expect an attack to be successful unless you have the positional basis to do so.  Premature attacks are doomed to fail and are a hope chess. 

A goal.