In reply to RankAmateur:
I tend to do, in order of preference:
1 - overtake stationary/slow moving traffic traffic on outside, if safe to do so, depending on what's coming the other way and amount of space (check for motorbikes/other bikes/impatient sales rep doing the same thing before you pull out). Make sure you plan where you can cut back in if you have to before you start.
2 - filter down between 2 lanes going same way, but ONLY if both are stationary, never when either are moving.
3 - very rarely and ONLY when traffic is stopped and there's enough room to cycle normally, pass on the inside.
For 2 & 3, I stop passing anything when the traffic starts to move again.
NEVER undertake anything larger than the average family car - anything bigger might not see you and won't be expecting you.
Watch the vehicles you're passing for indicators that they're going to turn and watch a few vehicles ahead for indicators, as other vehicles might come into your path to avoid them, etc.