I enjoy using improvisation when I'm quilting because it allows me to play with fabric and to deviate from following plans and patterns. It's a great way to quilt without concerns and worries.
That said, I thought it would be a good idea to let you peek into my thought processes and into the ideas of improvisation. The "rules" of using improvisation in theater work quite well for quilting, also. #8 is questionable--until you think about looking the quilt in the eye. Really look at the quilt. Really.
You're allowed to make a mistake. In fact, there are no mistakes.
And make do with what you have. There's no need to struggle with whatever is missing or whatever doesn't match or whatever anything. Just enjoy the available resources and go with whatever!
Most importantly, enjoy yourself. There's no right or wrong way to piece a quilt or to quilt it. Just make it work for you.