Advice on decision making...

I think that's the one ^

Something looks to be misssing...

Oh, "targets"

If you don't know a tactic, how can look for it in the first place?

Well, look for targets (pieces AND squares) that can be threatened...by your opponent and you.

Back to calculations for a min first...you want to look for any targets your opponent may have (of yours). Sometimes the best offense is defense.

Anyway, back to targets...

• Exposed King (not castled, on open file/diagonal/1 knight move)
• Material of higher value (knight vs rook)
• Undefended material (unprotected not just hanging)
• Important squares (can be a little complicated to explain)...weak (can't be defended by a pawn), vulnerable (only protected by King), allow access to opponent's camp (behind pawns), center squares, etc (but that's a few)
• Important Defenders (defend important squares)
• Material of low mobility (possibly trapping or making a piece worse by forcing moves with tempo and maybe improving a few of your pawns/pieces in the process)

That's probably a bad format and misssing a thing or 2, but it's a start.

Targets would be weakness(es) in the opponents position. 

A tactic the OP missed.  They spend a little over 4 minutes on this.  If you cant figure it out in 2-3 minutes then its a position you dont know.  Set it up using a real board and pieces, and try again.  You will be amazed at what a differ that will make.  If you still cant figure it out, then look at the solution.  Learn and understand what type of tactics it is, what caused the tactic, and how it happened.