The .243 with good 100 grain bullets will take any whitetail waliking today! That said, the .243 is the minimum caliber I'd recommend for deer. From there you could go on up to the big magnums, which you really don't need, especially if you are new to shooting. Someone has already mentioned the .308 and it is a really good choice too.
For someone who is just starting into hunting and rifle shooting, and even for an experienced hunter for that matter, I'd really suggest the .260 or 7MM-08. Both are really great deer getters, they have a flatter trajectory, so thay are great at short and longer ranges, and they do it with less kick than the larger calibers! Good luck!