Trace the pattern piece on the exact line it is drawn on the pattern. Do not give any extra space for overlap. Then fuse the pattern piece pencil line down onto the back of the fabric. You can see I use just the point of my stick iron to accomplish this.
Then you can cut the shape out with very sharp fabric scissors, giving extra fabric where you need to overlap. I also am careful to not fuse the pattern paper to the edge of the fabric.
What you are trying to avoid is having to remove the fused backing paper from the edge of your fabric. This can cause the fabric to fray as you will inevitably stretch the cut edge. So even if I cut my fabric to the exact size and shape of the pattern piece, since I don't fuse to the edges, I don't have to worry about the fabric fraying.
I also avoid getting the wonder under on my iron, mostly.
Also, it is a good idea to check your pattern pieces against your work before you fuse the fabric to the back.
Here is a WIP shot. I am loving this quilt!