Originally Posted by DrGoogle
Check out this youtube or google Applying to UC: The personal statement.
Applying to UC: The Personal Statement 2007 - YouTube
That's a long video...
But my input on the subject:
Start working on your app early. Start writing your essays before the app comes out (I think it comes out a month before it's due).
For the essays, they are different from common app essays, they are more detail oriented, a laundry list of accomplishments would be a basic idea but you'd probably want to whittle it down into a theme or something and craft a beautiful essay about it. A touching story about how you grew as a person usually will not cut it. (I heard this from an admissions counselor. My essays were like that and I got into UCLA.)
For ECs and awards, start thinking about the ones most important to you and who you are. There's only space for 5 ECs and 5 awards (I believe) so you probably want to choose the ones you've been in longest, most contributed to, etc. Don't include clubs where you were simply a member. For awards, fill up the 5 slots with your 5 best awards.
Don't submit it the day it's due. Submit it at least 3 days before. The server has been known to crash basically every time in the last couple of days before it's due. Sometimes they'll extend it, but I wouldn't count on it.
P.S. UCSD is known for having a less socially dynamic campus than other UCs, not sure if you might take this into consideration...