Use only two people (in good physical shape) to lift the robot; the 28"x38" footprint of the robot is not big enough to safely accommodate a third person. Any more, and they just become a "fifth wheel" to the process.
At most, a fully loaded robot with battery and bumpers can weigh in around 140 lbs, which is 70 lbs/person. Though high, it's not excessive for students/mentors who are in good physical shape. (Who else has ever mixed concrete for a sidewalk in their yard, using dozens of 80lb concrete bags? As long as you lift them correctly (and one at a time), they aren't unbearably heavy.)
Design your robot to be easy to lift up. If you are going to lift it by the frame, file it down well. Otherwise, handles on your robot work great; Team 228 installed four on our 2007 robot before the ship date. (If you are going to use bumpers, seriously think about handles of some kind.)
Build a
low cart. Not only will it make getting through doorways easier (such as after match, when arm/elevator/appendage is still sticking up), but you also don't have to lift everything as high. (The opening in the front of the cart is for storing our operator interface.)
Don't lift up the robot when it's on. Turn it off first.
If you need help, ask someone. Don't try to carry eight batteries at once. Get another team member (or two, or three) to help you.
Use common sense.