Most essays give you a specific word count. Follow this. Write out your essay and then check the word count. If you find you have too many words, go back and read through the essay eliminating anything that is not necessary or does not have to do with the topic of the essay. Watch for words like "that," which have a tendency to be overused. You can also remove any unnecessary adjectives that do not add anything to the whole of your essay.
Focus on what the topic of the essay should be. You do not want to give a list of your accomplishments, which will probably be on another part of your application. Keep focused on the topic and make your essay as personal as possible. Allow the reader to get to know who you are as a person while they are reading your essay.
You also want to be as specific as possible when writing your essay. You want to give details on why you want to attend this particular college, why you want to pursue a career in this particular filed of study. Do not give answers such as "I have always loved Texas A & M." Give specific details as to what it is about the college that you like. Show them you have done your research and really feel that this is the best college for your chosen field of study.
To make your college essay look as professional as possible, take the time to proofread the entire essay. Do not depend on the computer's spell check; your words may be spelled correctly, but you may have used the wrong word. The more time and effort you put into your college essay will show in the finished product. Have someone else read your essay as well. Sometimes another pair of eyes will catch something that you did not. They may also be able to tell you where something is unclear even though it seems clear to you.