Of course,practice practice and practice. But, it always good to catalog some ideas of approaching a position to recognize tactical possibilities in a position.

Ask the question - “What are tactical motifs in the position on the board”?

Most common motifs to look for are –

Another question to ask “Whats the ideal dream position I would like to reach”? . And, then figure out what is preventing that to happen.
So, lets try a process for a position.

First, try yourself. Then, move ahead.

In the above position, the major motif is back-rank weakness. The dream position black would like to reach is mate on e1.
But, the white queen can come to f1,after Qe1+.So, how can we exploit the weakness? How can we deflect the Queen?
The answer – Rxa3!! – a revolutionary move (as an author suggested in some book in relation to tactical blows).
It attacks queen- if queen takes the Rook on a3,then mate on e1 (Rxa3,Qxa3 Qe1+,Rxe1 Rxe1#).
If Queen goes to f1,then white is again mated (Rxa3,Qf1 Rxaq,Qxa1 Qe1+,Qxe1 Rxe1#). So, the best possible move for white is move the Rook,and give up queen. And, the end result is a hopeless position.

Now, give a try to below position(black to move). Answer will be posted in the comments.

Answer
What can we deduce from the position? The g-file is open, and black can give check with Rg6. The king can go to f1 or h1. If Kh1, then Qxf3+, Bxf3 forced and Rxe1 mate. But,king moves to f1. Then, Qh3++ mate.