Name and recognition is a fair place to start, but also google which universities are good in your preferred subject - a good number of universities are good in certain subjects but are not overall "big-name" unis.
Admissions to US universities is less grade-oriented than in the UK. Also, you'll study many subjects, and it is far from uncommon for students to change majors, so there is less focus on your particular subject of focus / major. What subject are you wanting to major in? Look at the kind of classes they offer, what opportunities they offer for your program, etc. I'm not sure what you mean about a grading system? You don't apply for a specific subject in the US, rather to the university as a whole. Generally, universities like to see greater accomplishment in one subject and some accomplishment in other interests, which can be extracurricular. This is moreso true, I think, in highly ranked unis.