I usually make one block according to the pattern and the fabric I will be using. That way I can see if the block looks the same in real life and it does in my mind. Sometimes my mind plays tricks on me and the block looks nothing as I planned. If all is well with block, that is the first block of the quilt. If I don't like the colors or something else about it, I will make changes .....and have often done that. I then use these "mistake" block in a scrappy sort of quilt.