I wrote it in my blog:
http://how-to-kongregate.blogspot.com/2007/12/dolphin-olympics-2.html

First of all, you need to have mega fast speed or star sliding wont work. You know how tail slides work right?; the faster you are, the faster you will go up after a tail slide. Star sliding involves the exact same thing, but I don't think the way you approach star slides really matters. Though always remember to approach tail slides at an acute angle or near horizontal.