Every writer has a smile on their face when they reach the end of a manuscript. I'm always surprised (and a tad disappointed) that there aren't spontaneous parades. Reaching the end is great, but then your inner-editor starts to niggle "Is it the right ending?"
Here are some questions I always ask before I snarl "Yes," at my inner-editor. Please remember, I write mysteries so many of these questions are genre-specific.
1. Is the timeline correct?
2. Have all the red herrings been revealed as such?
3. Is this resolution (i.e. the identity of the killer) stretching the boundaries of believability?
4. Is the final step to uncovering the killer's identity believable?
5. Have the sub-plots been resolved?
6. Does the ending come too abruptly?
7. Should the ending actually be 20 pages earlier, because nothing happens there?
8. If I was reading this book for the first time, would I want to read another book by this author?
If the answer to #8 is "No" then I've got a whole new set of questions.
How do you know your ending is the right one?