--I don't trust precuts so I rarely use them -- I prefer to cut my own (after washing the fabric to get the excess color out).
--I know that every piece of flannel shrinks differently so I prewash and dryer dry before I cut so I know they will play nicely together.
-- I rarely follow a pattern -- my eyes glaze over about half way through reading a pattern so I just figure out how to make it so it makes sense to me. I find that if I take a piece of graph paper and draw the quilt (or block) out I know how to make it by the time I am through.
-- I know the lines on my quilt mats are accurate because I measured them with the rulers that I use on them.
-- I don't trust 2 machines to have the same 1/4" so I measure carefully before going from one to the other to ensure I don't have block creep -- I use a 3x5 ruled note card to give me my accurate 1/4" and my scant 1/4".
-- I don't trust rulers of different brands to measure the same because the width of the lines is different so I either stay with one brand or mark the cutting lines carefully with tape.