Getting out of the back corners
This is an area beginners always have problems with. It is harder for beginners for a couple of reasons. Firstly, because of a lower skill level, it is harder to do. Secondly, because beginners don't get the rubber ball anywhere near as warm as advanced players, the ball doesn't bounce out of the back as far. You want to try and get under the ball by making sure that you bend a lot at the knees, and aim very high on the front wall. Make sure you have a full follow through. If you feel you can't hit down the wall, hit it high and hard into the side wall, to make sure it reaches the front. Good players sometimes slip their hand 5 - 10 cm up the grip so that you can get you racket behind the ball on particularly tight shots. This makes the 'lever' (your racket) a lot easier to 'flick' the ball down the wall. If it is super tight, try one of these two alternatives. Firstly, you can basically just 'scoop' the ball to the front by hitting with almost no backswing, and a big follow through. This wont get the ball to a good length, but it will get the ball to the front, keeping you in the rally. The other alternative is to hit the ball high and hard on to the back wall (generally a bit of a 'flick' with not muck backswing will do the trick). You are then a least still in the rally. But of course the best thing is to chop the ball off with a volley before the ball goes to the back! So, make it easier on yourself by keeping out of those unnecessary zones.