Practise, practise, practise. Just make up a rough sandwich with batting and two bits of waste material and keep quilting on it until it starts to look OK. You will eventually improve and continue to improve with each quilt. I was frightened at one stage when a friend got me to help her quilt some charity quilts - now I still get out the rough piece before I start, and do about ten minutes of 'loosening up' exercises on it and then get going on the quilt. Just be confident and consistent.