Lots of good advice above.

Being aware of those around you is very important. One thing that frustrated me last time I was out was inexperienced people in faster cars not being aware. This meant that I was catching them through the corners but on the straights, instead of easing off and letting me pass, they would accelerate away, only for me to get stuck behind them again in the next corner.

It's very easy to concentrate on your own driving when you're learning and lose track of others, but try to keep an eye on them and just let them go as soon as it's safe. It's much nicer to learn the lines and the behaviour of your car without the pressure of another car up your chuff.