When I first got my Motorola/Verizon/Google Droid phone, I thought it was broken because it wouldn't talk to my laptop. I tried plugging it in to multiple USB ports, resetting, searching for drivers, etc.
It turns out that it's really easy to get this working, and once you do, you'll understand something that's critical about your new phone: everything important shows up in the notice bar at the top of the screen.
When you plug the Droid in to a USB host like a laptop or desktop system, it brings up a notification (USB logo in the status bar). Place your finger off the screen, above this notice, and swipe directly down onto the screen. This will bring up the all-important notification menu. Here, you'll see things like "USB Connected" and various app installation notices if you've recently downloaded anything. Touch the USB notice now and it will bring up a dialog box that asks if you want to mount the SD card on your host computer. Press "Mount" and you'll have full access to the SD card from your system. When you're done, you can either repeat this process or just unplug the USB cable to force it to re-mount internally.