Have you ever struggled with pronoun usage, comma splices, or whatever the heck "subject-verb agreement" is? Guess what--you aren't the only one! Some problem areas are just so common, Andrea Lunsford of Stanford University actually compiled them into a list entitled "20 Most Common Errors." If you're struggling, try perusing this list. You may find that whatever grammatical concerns ail you are shared by a great many writers.
And while you're at it, take a look at the Resources for Writers page on the EIU Writing Center website. You'll find links to quite a few sources that will help you with all aspects of your writing process.
(If the links aren't doing it for you, feel free to visit the Writing Center and discuss your concerns with a real live person. Student, staff, faculty--all are welcome! And it's free!)