According to the admissions website a composite ACT score of at least 30 with at least a 27 in the Math and English components are enough for automatic admission. You must be in the top quarter of your class - if your school doesn't rank, your counselor should still be able to determine a rank for college purposes. You can't possibly be the first student to apply to college where a rank is requested. You must have also fulfilled the high school course requirements for admission. Look here
http://admissions.tamu.edu/freshman/admitted for specifics.
Blinn and Galveston are options if you don't make it directly to A&M. Blinn Team students can live on campus, participate in the corps and even take a class at A&M but they are not officially accepted at A&M until they have completed two years at Blinn - which is a junior college in College Station. After 2 years, if your gradepoint is a 2.75 (I think) you are automatically accepted to A&M. All credits earned at Blinn are transferred to A&M. Texas A&M Galveston is an extended campus of the A&M system. It and Qatar are the only ones where you can receive credit the same as taking classes in College Station. Texas A&M Corpus Christi and Texas A&M San Antonio, for example, don't count towards time at Texas A&M College Station (the main campus) and if you are enrolled at Corpus Christi or San Antonio, you can not just switch over and take classes in College Station. However, if you get accepted at Texas A&M Galveston - their admissions standards are a little lower - then you can switch and take classes at Texas A&M in College Station as long as you are still in good standing (GPA 2.0) after your first year.
But if you really want the true A&M experience and you qualify, go straight into Texas A&M in College Station. You can also apply to Texas A&M Galveston, but A&M has to offer you the Blinn Team option - you can't apply for it. Basically if you aren't accepted to A&M, they don't tell you "No", they don't wait list you, they might offer Blinn Team. You can always apply to Blinn Junior College directly, but it is not the same as Blinn Team that has the automatic admission to A&M and the same privileges of living on campus, etc.
Again, the website or an admissions counselor can answer all these questions more accurately than I can. My knowledge of Blinn Team and Galveston is from a couple of years ago, so don't rely on this as gospel.