Great advice on advertising!
I have something to add though that I've learned from glitchfinder who makes this mistake when advertising his projects (and it annoys me a lot)
When posting an add; never say, "The best project on scratch," because by saying this, your also saying; "this project is better then all the stuff you've worked so hard on, it's better than all of yours!" even without that being the intention.
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Make sure you post the ad at the right time. The majority (I think) of scratchers live in America, so make sure it's not the middle of the night for them when you post, so then they can see it.
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