When I took the girls to the doctor last week, I used some advice I had read in one of the twin books I read. Instead of lugging 2 baby carriers in my arms, I just plopped them into the double stroller and wheeled them around. This is probably one of the best pieces of advice I've gotten. Maybe you use a stroller at the doctor already, but I'm not so sure I would have thought of it on my own. It would also be very helpful even if your children are different ages. It just gives you a place to put them (and strap them down) so they aren't running 20 different directions. Give it a try.
On a sillier note, the girls got shots in each leg, and of course I held them when they were finished. It wasn't until I saw my reflection in the window of my car (after walking through the office, talking to the receptionists, and pushing my huge stroller through the waiting room), that I saw 2 Bugs Bunny bandaids plastered smack dab in the middle of my chest. Lovely adornment, wouldn't you say? Sheesh!