Step 1: Ask yourself, "What do I want the trick to look like?" Whether it is a string trick, a slack trick, or some other type of trick, Have this in mind before you start building your trick.
Um. All I have to say is no. That's seriously all I have to say...I don't know.
Lots of people try to make tricks when they only know several tricks like in Advanced Part 1, so none of their tricks are actually unique, they are just different versions of tricks like rewind, mcbride roller coaster, the matrix etc.
Hm. I actually did start making up tricks somewhat around that point. After that, I pretty much stopped learning tricks, but you're probably right.
Anyways, what I do is I just get into a mount, any mount. It could be a Double or Nothing, Wrist Mount, or a One and a Half Mount. Then do something, anything. Move the yo-yo, move the string, move your fingers. Hit that string. Hop off that. Put your finger there. Make the yo-yo go through there. Pinch there. Slack there.
Take the elements from tricks that you know and implement them into new tricks.
Or even, do a trick that you know and mess up. And try making up a new trick from your mistake.