Whitetail antlers go flat with the ears and aim forward with the points sticking straight up as you can see in the image to the left the tail is white and they have a bigger body than the Blacktail above. I have never hunted Whitetail before but I want to and plan on it but I like hunting Bleacktail because I think the antlers look a lot better and the meat tastes really good.
Mule deer have a similar looking antler to a Blacktail but as you can see in the image below they tend to be bigger. Mule deer are the biggest bodied of these three and are more desired to hunt that the other two. i wouldn't have to travel far to hunt mule deer as there are some in California but there are no Whitetail as I know of in California. I hope this information helps you identify the deer you see.