When putting a book together I always think of what Philip Larkin told his publisher when asked if there might be another book in the offing. "In the past I've always had 10 good ones and the rest were fillers. Well, I've got the fillers.'' Not all of us are so rigorous. We go ahead and publish our fillers and are damned. Larkin said he always liked to put a good one at the beginning and at the end of a book. I always look there before buying anyone's new book. If the last poem's no good they're in trouble. Another consideration might be to sprinkle your "good ones'' throughout the book, to give an impression of quality, or at least to spread out your "fillers'' so they don't gang up on you.
I like the picture he creates of how he goes about it:
My method at this time is to clear the room and place all my poems on pieces of furniture where I can see them. Now I stand in the middle, suitably coffee'd up, and attempt to conduct the storm. The idea is to make something greater than the sum of its parts by having all the poems cast an eye both forward and back - a virtually impossible demand of poems that are also required to stand on their own.