Don't be "that guy" that can't ride a straight line. Even safe random sideways movements make the person behind react, thinking there's road debris or something happening with the riders ahead. And the following rider wonders if the squirrely rider knows how to safely ride in groups.
If a gap opens up, I try not to close it fast, and then have to brake. If the pace isn't too high, with a possibility of being dropped, I'll very slowly accelerate, so the following riders can stay in my draft easily.
My biggest problem is pulling the line when the road is all small rollers. I can't use the speedometer to keep the same pace. And my HRM reacts too slowly to small hills.