Don't not forget to rise out of the saddle on a downstroke, because if you skip a stroke while standing up, or up shift too soon before standing, your bike will go right back into the front wheel of the poor sap behind you. Very rude.

I tend to punch the bottom of the stroke, sort of hopping, so my legs are somewhat straighter at 3 and 9 o'clock to support my weight, and pausing a fraction of a stroke now and then to maintain the gap to the wheel in front. It takes less energy to pull out of a pace line a little where you can be less anal about your speed and the extra wind will slow you down.