Why would you not want to add a personal snapshot at the top that sums you up and sells your skills and experience? Keep it relevant.
Look and feel
A CV should be easy reading, using the same font and point sizes throughout, with headings aligned and looking neat and tidy. If there is even one spelling error, this could mean your CV does not get considered.
Are your interests interesting?
Make sure your interests are a wise choice, and demonstrate certain traits that will appeal to an employer. Think carefully.