Here is a link that was started way back and has some info about what you need to do http://talk.collegeconfidential.com/texas-m-university/1923296-freshman-on-campus-housing-class-2021-p1.html
To be guarenteed freshman housing on campus, you have 30 days to apply for housing from the day you were admitted. If waiting for UT decision, which may be another 3 weeks if they go by the past two years schedule, then that may be too late for guaranteed A&M on campus housing. You can go ahead and apply for A&M housing, pay the $50 applcation fee (which is not refundable) and the $300 housing fee (which is refundable), then you will be in the system. Room assignments are based largely on priority date – which is defined as the date the housing application, including fee, is received
If you get accepted to UT, then you can cancel your housing at A&M and be refunded the $300 and refuse your admissions decision.
A lot of applicant choose their dorms by cost first. The different types of dorms vary in cost per semester. Choose which type fits your budget. The Commons has just undergone a two year restoration and will feature its own dining hall and convenience store. Mosher Hall is the Living Learning Community LLC in the Commoms. It is on South Campus and closer to engineering buildings but your first year classes will be all over the place.
A lot of applicants also like the Modual Halls. I have read that Walton will become co-ed and only Freshmen next year.