Like so many who start post, i am a relative begginer and hav a question.  This may seem rather obvios, but i'm curious;  To what extent should you be focussing on the options available to your oponent?  Obviously i know you should to some degree, but is it worth going through every single potential move they can make, or should you mainly focus on your options and rely on them being strong enough to deal with any resulting action?

If you are timed do a quick scan of the board.

If you arent timed going though all possible oponent moves is a good idea.

you must always analyse what your opponent's options are, but you don't need to look at every single move. Try looking for a series of 2 or 3 moves that they might make to gain position or material. To dismiss your opponent's moves and rely on your own attack is seriously flawed. If you are forcing his moves, then fair enough, but this is not an option in the opening and middle game.

When playing Chess, you should be considering what you and your opponent are playing for and try to make it harder for your opponent to accomplish his goals while moving forward on your own. The extent you should look is dependent on the time control. If its a 1 minute game, you won't have time to figure out deep plans your opponent is making but you can spot 1-3 moves ahead such as immediate threats to a quick build-up. If you're playing a blitz game such as 5 0, then you have time to think of plans for both sides and be able to look 1-3 moves in advance. If its like a tournament game with 2 hours for each player, then you should be basically playing two games; your color and your opponents.

You can never just hope your move was good enough to meet anything your opponent responds with -- you always have to check to see what they might play on their next move.  This can be troublesome at first, but will get easier with practice.

Two good ideas for beginning players:

It's always always worth looking at every check and capture available to your opponent.  If you only look at one or two possible captures or don't even notice a check your opponent can play, and they catch you off guard with a check or capture, then you have no excuse, you were just being lazy.

It's always worth trying to find your opponent's most "annoying" move -- that is the move you don't want him to play against you.  Pretend you're playing the other side for a moment -- what's the best move you can come up with?  It's never worth looking at moves you hope your opponent plays or moves that wont be good for them to play.  Always assume they'll find an annoying move to fight against your idea.

Practice makes both of these things easier and more automatic and is worth it.

Cussing on the enemy is the way to go.