Speaking from experience here...
If you don't have a pretty powerful zoom, you'll need to be really (and I mean really) close. Are you photographing tame deer? That would be ideal. If you're after wild deer, I'd recommend a ground blind or low tree stand and camo. Then just set your camera for the lighting conditions you're in (wooded, shady area; open sunny field, etc...) and be ready. If there's a multi-shot function on your camera I'd use that, and just hold the button down and fire away.
I borrowed a friend's tree stand this past fall, and got in before sunrise. I waited and waited. At the time I only had the kit lens on my RebelXT, so not much zoom. Some does came out right after sunup, and they were fairly close and not moving fast, but my telephoto wasn't powerful enough to really capture any detail. I'm going again this spring now that I have a better lens
