Preventing blunders?

The vast majority of my games still seem to be decided by blunders. I regularly use tactics trainer to improve my tactical understanding. However, in terms of my thought processes do I need to consciously make a blundercheck before every move?

A couple of questions:

You mentioned "tactical."  Are most of your blunders of a tactical nature?  Are they time pressure related? 

Do you make as many when you play at slower time controls, and during slower over-the-board games, compared to faster, online blitz games? 

Do the blunders happen in all phases of the game, or do you find yourself making more of these blunders during, for example, the opening and middlegame?

Are they beginner blunders, that you at your level shouldn't be making at all?

I ask these questions not because I'm looking for an answer.  These questions are ones you should ask yourself.  Because if you examine and are able to determine exactly why and when you make them, you're well already on your way to start eliminating / reducing them.

Notice that you have not lost a  game  where the time is over 15 minutes per side.   If you are not using a chess engine, that is a very good sign.  Continue playing games where  you have at least 2 hours per side.

Blitz and bullet and other rapid transit games that are less than 1/2 hr. per side  are used by stronger players to practice their visualization pattern memory banks.  This type  of game  does not really help players that  are under 1600 OTB.

Another help is to make a Before I Make A  Move List:

1. What is my opponent's threat?

2. Are any of my pieces or pawns or my opponent's undefended?

3. Remember pawns cannot move backwards.  Any pawn move changes the position on the board permanently

4. Remember pieces CAN move, defend, capture and check backwards

Keep this list with you at all times.  Memorize it and add to it as you see  problems and other things you miss in your thinking during games.