Things to Do in Your Statement:

• Write with perfect grammar and spelling.
• Be Honest
• Give the impression you are interested in this subject and will be motivated to study
• Give the impression that you will be a likeable student to teach.
• If possible, Make a link between what you have done in your spare time and the course you propose to do

Don’t

• Be arrogant. You have to give a good impression of yourself without appearing over the top. It is a fine balance, which many students have difficulty doing.
• List your hobbies with little explanation ( I play football, I watch TV e.t.c)
• Say in your spare time you play computer games (yes, I have seen drafts with sentences in like. ‘My favourite hobby is playing computer games’
• Feel obliged to excessively promote yourself (your not a politician standing for election. – Your admission to University does not depend on how many swimming badges you received at the age of 11.)
• Put in tired cliches “It’s always been my life long dream to be an Economist…” (no body has this dream)
• State the obvious all the time. “I read newspapers, which gives me upto the date information about the economy”
• Make sentences excessively long

More ideas here on writing a personal statement

If you are still unsure what to write check out this model College application letter , which is apparently real