Get a tactics book and practise. You can also use tactics trainer here or chesstempo.com . When you solve exercises on a board you should solve the problem in your head without moving the pieces (!). Reason being is that in a real game you can´t move the pieces either when you are thinking about a move. The method of thinking and solving problems is always the same. The following text is something I wrote to someone rated around your rating on this website. It is a basic scheme how to think about a certain position and how to find the "best" move.
Step 1.
Understanding the position
First of all you need to understand the basic aspects of the position. What is going on should be your question, who is better and what are the main characteristics? For lower rated players it is the best to just look at the following things in the position:
-material (balanced or is someone material up?)
-king safety
-unprotected pieces
-typical motifs of piece placement (for example are king and queen on the same diagonal so maybe you can pin them? over time you will notice those patterns immediately without needing to search them in the position)
-piece activity and space
(-weak squares)
When you looked at all these components (you will notice that expert players are so good that they subconsciously notice all these points without even needing to spend much time on them) you will get a pretty decent picture of who is better in the position. Only after you understood the position you can really try to find the best move because in order to find the best moves you need to think of all these aspects or at least consider them in your thought process.
For example when you have a position where white has huge material advantage but a weakened king it is obvious that black HAS TO try to attack whites king because if he does not do that he will just lose the game on long term because he is material down. There are thousand of different szenarios so just try to understand the position and try to understand what matters in the position and you will be able to find good moves there.
Step 2
Find Candidate Moves:
After you understand the position you need to find concrete candidate moves for the side you are playing. What are candidate moves? Candidate moves are moves that come to your mind when you look at a certain critical position (after you did step 1). It depends on the position how many candidate moves you can find. Sometimes the best move is even obvious, in this case you would only have 1 candidate move and it would also be the best move already. But in case of harder positions (tactical or strategical) you need to find several candidate moves(normally around 3). So again what you do is you look at the position and first try to find out the basic characteristics of the position(over time you will get really fast at it so you do it already subconsciously. its not like all strong players think in these 3 steps but they do it subconsciously, its how their thought process works), then you try to find candidate moves based on the aspects of the position. Is the enemy king weak, are there certain patterns that might occur? Then you look for moves which attack the enemy king. Finding candidate move is just about finding several logical, good looking moves in a position based on the characteristics of the position. Its also important that you do not analyse the candidate moves you choose, you will do that in step 3.
Step 3
Analysing your candidate moves
In this final step you analyse every candidate move you picked in 2 shortly(! you do not want to waste all your time on a move which finally is not good). So you just think of for example candidate move a) and try to find your opponents best reply to it. Normally you will see after short time that your move is either promising or you can not find any win or good chances with it. In the second case you just throw this move away. This you do with all moves, at the end you should have a favorite move, which is also the move you should then play in the game. In tactic puzzles there is always a "winning move" so one of the candidate moves that are in the position HAS to be the winning move. In a real game you play it might be that you do not find a winning move, in this case you try to find the best move based on your understanding of the position (step 1) and your analysis of the move (step 3). Important is also that when you are sure that you found a good or even the best move you check it again to make sure you did not do a mistake in your analysis of the move(maybe you missed a good resource by your opponent or you miscalculated). A case that can also happen is that none of your candidate moves looks winning or at least you did not find a win. In this case you either missed a winning line in your analysis to the move or you did not yet find the right candidate move. That would mean you go back to step 2 and try to find another candidate move. Remember, at least in a tactical puzzle there has to be one best/winning move, so you just need to find it.
I've read that improving your tactical ability is the best way to improve your overall play, so that's what I'm trying to do. When doing the tactics, should I try first to visualize all the moves in my head, and then play it out? Also, currently I just do a random assortment of tactics on chesstempo and chess.com. Will that even benefit me, or do I have to train the tactics in a certain order / under a certain category to really drill the patterns?
In short, how can I practice best?