Too often we leap on our trusty stead to exercise our legs and duly switch off everything above the waist. This high-level inactivity is fine for cruising 'the smooth' but gets you in all sorts of bother as the terrain becomes more technical. There are different ways to attack obstacles on the trail but the principle remains unchanged - to ride smoothly over these gnarly bits. The answer lies partially in the maths. You are around six times heavier than your featherweight scandium bike so it is inherently sensible to throw it around rather than your body (carefully of course - it's expensive and sleeps inside). Correct bike set-up is essential to allow you to control the beast. The general aim is when in the just-riding-along position for your arms to be slightly bent and taking some of your weight. If this isn't the case then visit your local bike emporium. Once this is sorted, think about dialling up one of three 'riding modes' when out on the trails.
Often deployed on a Sunday after a hearty breakfast of french toast, bacon and maple syrup. This technique is quite natural - make yourself like a dead weight perched on your seat getting bounced around by the bike. It is used by too many riders too often, but is appropriate on small bumps and corrugations. Even in this passive mode it is important to get off your seat and keep your arms and legs relaxed so they can absorb the bumps.
... to be used when the terrain is tricky but the wheels can still freely roll over the obstacle. The trick is to anticipate how your front wheel is likely to behave and help it through the movement. As you zoom towards a speed hump:
... for when you need to initiate an action that would not otherwise have happened. These gravity defying moves are used when wheels cannot freely roll over an obstacle - like bunny hopping over a drain at speed or tackling a super steep drop-off with a stiff power stroke to launch you off the edge. But that's another story. Bon courage mes amis.