More on pace lines If you're next up to pull the line there are a few things to keep in mind:
Note the current speed -- and keep it when you get up front.
You've not been pulling so the draft has made your task easier -- don't outrun the cyclists moving off the front.
You're actually better able to see things further ahead than the lead; call out obstacles like car-up, dog-right.
If it's time for your swig, take it now; don't wait until you're up front.
Keep an even pace with the lead. Don't let the slinky effect begin with you! The rest of the pace line will never recover outside of dropping back and establishing their own pace line.
If able due to mirrors, keep an eye on those behind you and warn the lead if you're dropping others.
Prepare yourself for taking the lead; guess about where the current lead will come off and mentally prepare yourself for a smooth, consistent turnover at the front.
If you're in a double pace line and know the other cyclist is stronger than you, let them know what you're comfortable doing (i.e. how long you'll be up front).
If in a double pace line the left-most #2 cyclist is in the most vulnerable position as the leaders transition off to the left. As the right-most lead moves left, if the left-most #2 will move slightly right (to the middle of the road), then the transition will go quicker, smoother, and safer. Remember, the leads are likely tired after a good pull and may be a little more erratic than usual.
If you're in a higher-level group than you usually ride with (e.g. moved up to 18 group), then you've likely figured out that the 18 group will ride at 19.5 to 20 in a pace line in order to average 18 over the length of the ride. This may be a lot for you. In these cases, see if you can stay on front for 1 min and then peel off. The mental prep for this as you are #2 in line is key. A minute should be doable. Be ready.