Can you tell me how to do any neat Blogger tricks?

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Can you guys tell me how to do any neat Blogger tricks to make my blog look better. I need help with adding gadgets. It only shows so many when I add them to the blog. I really can't understand. Also I would like to know where to add my HTML. I could probably do it on my own, but every time I try to experiment with it, it comes out all wrong. Any suggestions? Also do you guys have any suggestions on neat widgets to add to my blog?