How to deal with roundabouts - overtaking through:
If the queue approaching a roundabout is very long in the left hand lane, or there is traffic moving very slowly in the left hand lane, then you can overtake through the roundabout by using the right hand lane to go straight ahead. You can exit in the left or the right lane. However to be safe, only overtake through a roundabout if you are 100% sure that there is a two lane exit, otherwise you may have nowhere to go.
Speed control in the roundabout:
Roundabouts are just a series of bends, so to control the speed properly around them you will need to balance the gas against the steering (piece of string method). Once you've pulled away safely into the traffic flow, and got to a reasonable speed, then ease off the gas as you turn in to any curve, ease on the gas as you straighten. For each steady curve of the lane, you should have steady gas. If you just accelerate all the way through, there won't be enough time to steer properly. This will lead to not being able to stay in lane.
Keeping in lane:
When going straight ahead in the left lane it is very easy to cut into the right lane on the latter part of the roundabout (straight-lining) . To judge your lane position on left curves look to your left front side, for right curves look to your right front side. Try to keep a constant distance from the the roundabout centre, and imagine there is a truck next to you in the other lane.
Roundabouts often don't have lane markings on them, but you will often see small lines of tarmac that you can use to judge where a lane should be. When going straight ahead you will see on most larger roundabouts that there is an area on the far left that no-one ever drives into. it's normally full of debris; try to avoid this area if you can.