One of the most important tools that writers can use is the ability to read assignments aloud. Reading assignments aloud helps to catch grammatical errors, run-on and incomplete sentences. Reading aloud helps writers find portions of their writing that need improvement.
When you finish a writing sample, take a break and step away from it. Come back several minutes later and read it out loud to yourself, incorporating the appropriate pauses for punctuation: short breaks for commas and longer ones for periods. If you struggle through reading a particular sentence or phrase aloud then that is a good indicator that your writing could be made better.
I can not tell you how many times I have had a student read their assignment out loud to me and watch as they begin to self-correct problems in their writing. Hearing yourself read your own work can substantially decrease the number of errors in your writing and help to improve your writing ability.