Here are some guidelines for checking correct pronoun usage:
print out a hard copy of your document
mark all the singular pronouns with a red pen and mark all the singular subjects with a red pen.
mark all the plural pronouns with a green pen and mark all the plural subject with a green pen
Make sure each pronoun agrees with the person (1st person, 2nd person or 3rd person)
Check to make sure that the pronoun agrees the number (singular or plural)
Try to have someone else proofread you document