Part of my work at the contract signing meeting is getting the couple to start thinking about the timeline for the day. Generally they'll know when the ceremony starts and when the dinner starts (sometimes that's flexible) but other than that things are fairly open for discussion.
I discuss the day with them, determine what their expectations are and considering the logistics (how many group photos roughly, how much travel we're doing between venues) give them rough estimates of how much time should be scheduled for each portion of the photography for the day. E.g., I might suggest 1 hour for getting ready photos at the house, 30 minutes for formal group photos etc. I also find it important to emphasize that traveling between venues and even between zones at a given venue should be considered and that a little extra buffer time should be included if possible.
About a week out from the wedding, I will ask to see if they have a slightly more firm schedule for the day--half of the time they do. If I feel like we're not quite clear on the schedule, I'll send a mock-up and get their feedback about it.