(Gratuitous cute pic alert!!) I started making my antlers by tracking down this set of real whitetail antlers in the wilds of eBay. Whitetail antlers in particular are more on a human scale, as opposed to say, mule deer or fallow deer antlers, which can be huge. I made a paper mache version of these antlers by taking a positive cast of them in Celluclay.
I also needed plenty of reference photos, for which this book (found on the clearance table at a local bookstore) was my main source. The picture on the cover is particularly helpful. (Gratuitous factoid alert- I also learned from this book that antlers are the fastest known growing tissue in the animal kingdom, growing at a rate of half an inch a day.)
(Gratuitous factoid alert- on a trip to Wikipedia to check that my antler terminology above was correct, I learned it is now believed antlers act as parabolic reflectors, vastly improving the hearing of their wearers. I'm not kidding. We'll see if paper mache antlers can do the same!)