The introduction to your thesis is probably the first thing your examiner will read (after they’ve checked your bibliography, of course, to see whether you’ve cited them!) so its important to get it right. That’s why its often said that you should write your introduction last, after you know what you’ve done and where your thesis actually went rather than where you thought it might go three long years ago.
Here are some words of wisdom from one of the best-known writers on thesis writing. Check them out.