I have a 05 Honda Odyssey minivan.
What do I look for in a cartop carrier? I assume they all come with the proper connections for the rails on the roof. Do I just look at size and price?
I don't know what you're planning on carrying, but I would strongly recommend going with Yakima or Thule systems. Both make quality products that are very flexible in the applications and types of loads, and are quality products. If you're looking at price, yes, they are expensive. But do you want your stuff blowing off the top of your car at 70 mph? I have a Yakima system that I got used (through Craiglist, I think) several years ago, and then augmented with parts to fit my particular car. I've carryed 4 bikes plus a big bag of clothing, at cruising speeds, and it was rock solid. Proper installation is a must, of course. YOu can go on-line to either company's site and see what you need for your vehicle. You can also go to REI and talk to someone knowledgeable; I think they sell Yakima.
Steve makes a great point...and this is the reason why I am a Thule fan for both my bike carrier and rooftop carrier. Some of the other stuff is flimsy and leaks if raining. Yakima is good too.
"Sean McDonagh Racing"
Get a unit that locks securely, both to protect the contents from stealing and also to keep the top from popping open in transit.
THULE and Yakima are great choices. A nice comparison chart can be found at http://www.cartopcarriershops.com/comparecartopcarriers.html. The chart lists prices/sizes/volumes and also whether the carrier opens from both sides.
It's nice to have the cargo on the roof to leave the hitch open for carrying bicycles.
Finally made it to REI and got the info I was looking for. Basically, I first need to get crossbars for my roof. The Odyssey, for some reason, comes with the side rails, but no crossbars. They guy said there was really no difference in the Yakima round bars and the Thule square bars for carriers.
Then, either carrier brand will fit on any crossbars. Bike racks and whatever else also fit on the crossbars.
I quickly looked into the Honda crossbars, and it seems the price is about the same as Thule or Yakima--probably around $200. I think the Honda uses screws to attach and the others you can get with locks. There is some indication that the Honda crossbars are not as thick and strong as the aftermarket brands, so I'll go with one of those.
Thanks for the notes.