Believe it or not, colleges are looking for reasons to accept you, not reject you. With this in mind, most schools will "superscore" the SAT. That means they will accept your highest sub-test scores across all administrations. For example, if you take the test twice and you score higher on math the first time, but higher on evidence based reading and writing (is it just me, or is that a ridicuous sub-test title?) the second time, the college will only factor in those scores when reviewing your application. There are some schools that are starting to supersocre the ACT, but this is not as widely practiced as with the SAT. You can check here to see what your college recommends regarding test practices.