I do a lot ‘URL buttons’ where on a page or relate list I create a button that pulls / scraps fields from the current and relate objects and fill in the new record form. Stuff like Contact ID, Account ID, etc. that sometimes standard and custom objects don’t automatically pull over. Also good for creating record names without using workflow! Invariably I run in to some encoding while looking at samples that makes me scratch my head.
Anyone could find this from Google but this is a great resource for looking up all those ‘percent 3’ blah blah blah that Salesforce.com and other websites/applications use to put special characters in the URL.