No folks, you don't maintain a constant effort. You go hard on the hills and take it much easier on the flats.
When you're riding with folks you aren't real familiar with and you're leading, you come into the hill at a steady pace, then start working your way down through the gears while increasing your pedal effort. You hopefully have some idea of your limits. Ride strong, but don't exceed them. Don't worry if people go around you. Try to follow them, but don't stress over it. OTOH if they don't pass you, keep an eye on them in your mirror. If they start to drop off, reduce your pace until they don't. You should all get a feel for what the other riders can take and each match your effort to that of the others. You want to try to build a cohesive group. That's the sort of person others like to ride with.
On the flat, when you hit the front, hold your speed and cadence. Peel off before you get tired. Doesn't matter how long your pull is compared to those of others. It only matters that you pull steady and not too long for you. Very important not to increase the pace! That can be tempting sometimes, but don't be that guy.
As you go over the top of a hill, don't accelerate like you would solo. Hold back a little until the back of the line has cleared the top.
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