I second JulieR's suggestion of scissors. I am too much of a klutz to use the rotary cutters. I do use templates for things that aren't easy to "eyeball" match -- I'll make one template the size of my piece, and one the size of the piece plus seam allowance. For cutting, I can draw around the edge of my cutting template with a chalk pencil and just cut on the line; maybe a friend, spouse, older child would help you with that? Then for sewing, I butt the edge of my sewing template against the last seam sewn, and draw a chalk line where the new seam will go.
I hate to admit it among such accomplished quilters, but I also sometimes use a larger seam allowance than 1/4" when cutting, especially for things I haven't done before. An extra 1/8" or even 1/4" can hide a lot of boogers.