When Your Work is Ready to Submit

Have you workshopped it? (Some people do sell without workshopping, but it helps to have other eyes look at it).
Do you know where it will go in the bookstore? (If you don’t, don’t imagine that someone else will be able to figure it out necessarily.)
Do you think it is better than Harry Potter? (Don’t send it in if you have wildly inappropriate expectations about mega-bestsellerdom).
Have you looked at agent websites? Do you have a list of people you want to send to?
Are you revising it on a micro-level?
Have you started something new?
Do you know what problems there are with it that you can still fix? (Don’t send it in if you can make it better.)
Have you changed so much as a writer that selling this book would get in the way of a better career? (Don’t send it in.)
Are unrelated people asking you if you’ve submitted it? (This is a good sign it’s ready to send in, though not the only sign.)
Are you fiddling with it regularly, changing things back to what they were before, and then back again? (Time to send it in.)