I would have to recomend studying the public lands by getting yourself some good maps. One of the better choices for maps is by a publisher called DeLorme. They make atlases of various states that show all land ownership by color codes. Orange is BLM, State lands are blue, etc.
Unless you can buy actual BLM maps for the area you draw. One key to accessing public lands is that it has to be accessable by a "publicly maintained road". Like a county road, state highway, etc. If a sign says "P{rivate Road", you cannot drive on it even though it accesses public lands. Hate yto see you get in dutch for tresspassing.

Most importantly, get the rifle out and practice 200+ yard shots. Antelope won't let you very close. Especially after they've been shot at for a week or so.Put some shots on paper AFTER you get here too!A good range finder is an essential piece of equiptment too. You've got to know the distance to know the shot!

I guess there is one more thing. Don't tie to the hood of your truck and carry it back to Iowa expecting fine dining. Antelope needs to be field dressed, skinned, and chiled down as soon as possible. Wash it off real good too. You do this, let it age for 7 - 10 days, and you will be eating some of the best fare the prarie can provide.

Good luck, and good hunting.

p.s. Antelope ears are about 6" long and will give you an idea of antler length. I agree to look for mass and prong length. These add considerably to the scoring of your trophy. Width of horns do nothing to score, just might look cool!