Bouldering techniques - bad landings
Bad landings from falling or jumping are probably one of the greatest dangers to a boulderer. A bad landing can result in soft tissue injuries, particularly to the knees and ankles, and more extreme injures such as broken bones. Consider all of the dangers of the landing before starting the problem and carry out precautionary steps to improve the safety margin.
One of the only times it's better not to use one is when the landing is a smooth sloping surface so the mat is likely to slip away
It's usually very advisable to use a mat. One of the only times it's better not to use one is when the landing is a smooth sloping surface so the mat is likely to slip away. In such circumstances it is better to land on the ground in control than to fall onto the mat and then slip wildly out of control. When the mat is covering a hazard (such as a rabbit hole, partially submergred rock, tree rootes, etc) remember that they are there. The mat will be less 'forgiving' in these places.
You're aiming to stay relaxed so that your muscles can absorb the impact force when you hit the ground. Simply bend your knees and relax. In extreme cases where you might be falling at a strange angle, you may feel that you are going to fall over or need to run out of the fall. This all helps in the dissipation of the forces to keep you undamaged.
Cleared for landing
Clearing the landing of small stones and sticks is totally acceptable but if you do any more than this you are changing the environment which is a big no-no. We must maintain the environment in its natural state as much as possible. If you need to move any large tree trunks or stones out of the way, remember where they came from and put them back afterwards.
This is not really down to you, but if you spot well then you can only hope that you will be properly spotted in return. Small, light climbers are easier to spot than larger, heavier climbers who may prove to be hard to control if they fall towards you.