How do I create sharp, tactical positions? It is said that you shouldn't simply look for combinations every move; rather, you should create positions that tend to create tactical opportunities.
But what does this actually mean? I think my calculation is pretty good, and I strongly prefer to be in tactical positions whenever I think I can out-calculate my opponent. But how do I actually create these tactical positions? I play 1. e4, I play gambits, but these aren't always accepted, and a lot of them have calm positional responses. And sometimes I find myself in a quiet middlegame where I don't know what to do apart from shuffle my pieces because the position doesn't lend itself to tactics and combinations.
What method(s) should I employ to turn a calm position into a sharp one? Does the method of doing this change when my opponent insists on quiet, positional chess?
There are two key principles:

Tactics can only flow from a superior position
Dissipating tension early is usually bad

What these tell us is that, first, it is important to follow sound general principles in the opening and early middlegame. So, develop your pieces, get your king safe and try and control the center. Developing tactics is going to be much more difficult if your pieces are not developed, your king is unsafe or you don't have control of the center.
Second, if every time your opponent makes a threat or offers an exchange of pawns or pieces you tamely exchange then it is going to be more difficult to generate tactics. Instead you should try and counter with threats of your own. Ignoring one threat and countering with a threat of your own will automatically increase the complexity of the position and make it more tactical.
There is a third important principle which materialists often struggle with and that is to view the values of the pawns and pieces not according to some fixed 1,3,5,9 system but according to what those pawns and pieces can do in regard of the current and possible future positions on the board.
Now for an example from the Closed Sicilian. In the Open Sicilian there is a tactical melee from the third move when white plays d4. There are captures and threats and lots of tactics. By contrast in the Closed Sicilian white avoids an early d4, there are no exchanges, open files or big tactical threats. It is all positional manoeuvering for control of the (closed) center.
[fen &quot;r1bqk2r/pp2npbp/2npp1p1/2p5/2B1PP2/2NP1N2/PPP3PP/R1BQ1RK1 w - - 0 1&quot;]

Here it is white to move. Both sides have almost completed development. Black has still to castle and both sides still need to develop their queenside bishops. The only capture threatened is BxN by black but that isn't going to happen. No way is black going to exchange their pride and joy, the Dragon bishop. The struggle for the center is intense. Black is currently threatening to play d5 and, as all Sicilian players know, if black can play d5 then they have equalized and, in the minds of most Sicilian players are already halfway to victory.
To continue the fight white must stop d5 and the best way of doing that is with Qe1 lining up the queen against the king and so pinning the knight against the king is the e pawns are exchanged after d5. Black castles renewing the threat of d5. Now white has no way of stopping d5. All white can do to stop black equalizing is to come up with a counter threat but what? There are no obvious threats white can make, no obvious tactics.
The answer is to offer a pawn sacrifice with f5. On the surface it looks like black can just win a pawn with the obvious exf5 (gxf5 looks much more dangerous) but this is turns out to be a losing blunder. Better is to plow on with d5 anyway and maybe even offer a counter pawn sacrifice. Play could continue:
[fen &quot;r1bqk2r/pp2npbp/2npp1p1/2p5/2B1PP2/2NP1N2/PPP3PP/R1BQ1RK1 w - - 0 1&quot;]

1. Qe1 O-O 2. f5 d5! (2...exf5? 3. Qh4! {and black is in trouble}) 3. Bb3 c4 4. dxc4 d4! 5. f6 Bxf6 6. e5

and what was a calm, positional struggle has suddenly exploded into a highly tactical game where lines are opening up, pieces are hanging and you better be able to calculate.