When I was learning here is what I was told:
Like it - 1 yd
Love it - 2 yds
Crazy about it: Background fabric - 2-3 yds
Main fabric - 3-4 yds
Even focus fabrics take only 3-4 yards so you will probably be safe there. I also buy discounted fabrics for backings and usually get 5-8 yards depending on what style of quilts I am currently working on.
Hope this is useful.