Sequencing is the consideration of the order in which people navigate an obstacle, particularly a technical rappel.
Groups with varying skill levels
In groups where some members are less experienced, the most experienced member is generally the last to descend the rope as he must "clean" the rappel rigging such that it is both safe to rappel on and retrievable from the bottom, and he must do so without any double-checking by team members. The second most experienced member of the group is often the first to descend as he must rappel without a belay (or set up a top belay), navigate the drop without any coaching, and be sure not to rappel off the end of the rope if the length isn't long enough.
The technical requirements are much less demanding for all other members of the group as LAPAR can assist with correctly rigging for rappel, and the first person down can provide a fireman's belay and coach any tricky sections of the rappel from the bottom.
When the strength of an anchor is in question, the lightest experienced member of the group generally goes last without any backup. For everyone else in the group, a meat anchor backup can be provided in case the anchor starts to fail.
When a short or easy rappel is followed by a longer or difficult rappel, the group may be forced to wait for the second rappel for an extended amount of time in poor conditions such as a cold pool or small ledge if everyone rappels as soon as a rope is available. One small example of this is the pool between R2 and R3 in Pine Creek; there is often only enough room for 3-4 people to wait for R3 at the base of R2 without standing in water. To solve this problem, group members should only descend the first rappel when the waiting area for the second rappel is sufficiently clear.
A small drop with poor anchor possibilities can be rappelled by everyone in the group except one skilled down climber who meat anchors them. This technique saves the time and resources to make a difficult anchor.