What is the better way to stop blundering all my games? I am on the road that starts from the "Beginner" stage, trying to leave this "town". I know and understand the rules, I also understand most of the "classic" tactics. I am able to reproduce some mating patterns (and to understand them I think).

But yet I have some difficulties to leave the "Beginner" town: I blunder often, mostly because I overlook some possible moves from the opponent (a little bit like if I was playing "alone").

It is very difficult for me to force myself to consider all the possible moves of the opponents. Please note that I play mostly on computer (either against the computer, or in live/online chess against other human beings).

So the question is: what is the better way to stop blundering all my games? 

Should I forbid myself to "undo" my moves when I play against the computer? How should I read the board? Is there a standard way of forcing oneself to consider all the consequences of a move?
I am on the road that starts from the "Beginner" stage, trying to leave this "town". I know and understand the rules, I also understand most of the "classic" tactics. I am able to reproduce some mating patterns (and to understand them I think).


Based on your information I think I can safely assume that you would see those blunders if someone pointed them out. This is an important fact that helps me to recommend you the solution.


  It is very difficult for me to force myself to consider all the possible moves of the opponents.


You should not do that-it requires too much mental energy and wastes too much time. 


  So the question is: what is the better way to stop blundering all my games? 


Much better approach is to understand what your opponent's plan is and to search the best moves he can play to implement it. This requires the ability to understand the position that arose on the board, and a fair amount of objectivity. To achieve this start with the following actions:


Learn the basic moves and middle game themes/plans of your openings-I find Starting Out series to do a wonderful job, I use them myself too.
During play detach yourself from your emotions and use your knowledge of openings, tactics and middle game plans to evaluate quality of the opponents moves. Ask yourself questions like "Where does my opponent lead the attack?" , "What are my weaknesses?" , "Is this move played consistently-does it support opponents plan or is it a deviation?". 
Tactical mastery greatly reduces blundering. Try to solve puzzles and try to improve this part of the game by constantly playing.



  Should I forbid myself to "undo" my moves when I play against the computer?


NO!!!

This is the best approach you can use-if you make a blunder just memorize that it is a bad move. Undo move and try to play a better one based on your own knowledge. If you fail to find satisfactory move, just consult books I have recommended or setup a position on your computer and order it to analyze. This will provide you much needed experience in playing that position, and at some point you will simply start to "feel" the good moves.


  How should I read the board? 


Watch the entire board and look all the squares opponent's piece attacks ( the piece he played last with ). This is important, I have this flaw in my own game too and it creeps in because you do not "respect" opponents attack enough-believing that you have faster and stronger counter-attack or simply believing that your game is much better and he should resign instead prolonging.


  Is there a standard way of forcing oneself to consider all the consequences of a move?


Use the combination of all the above advices-watch all the squares his last playing piece attacks and try to understand what role that move plays in his overall plan. Knowing the basic moves of the opening will help you to survive 15+ moves, and knowing basic middle game plans will reduce your calculation time since you will be able to assume with great accuracy what is the point behind the last move your opponent played. Also, by knowing your opening and its middle game basics, you will find your counter moves much easier and much faster.

Tactical skill is also important here, and just by continuing to solve puzzles you will be able to find hidden threats faster, both for yourself and for your opponent-which will strengthen your evaluation accuracy. 

Hopefully this will help, leave a comment if you need further help.

Best regards.