You left out my favorite! Be waiting in line at opening and stay until closing!I find that even if I'm not looking to buy anything, I just really enjoy looking at the animals and talking to the vendors.
As far as making purchases, I'd definitely want to be there first thing in the morning, to have better selection. While you might be able to get a lower price with at least some vendors if you are close to closing time, I think the real prizes are the top notch animals, which will already have sold. What's the point of getting a bargain on an animal you would never have purchased if you'd seen the one on the next table over that sold a few hours ago?