Hi simple rules that I use.
1. use chinese hackles or soft genetic types they are easier to double.
2. always double your hackle many explanations on here I just do as I go as I feel the scissors method can damage your hackle if you are not careful.
3. catch your hackle in by the tip and fold back, this helps with bulk and stops your hackle pulling out.
4. sounds daft but be the boss of the hackle, it will naturally want to do its own thing so wind it squarely and it touching turns for best results.
5. Get a lesson or find someone who has been tying for a long time there are loads of little tricks to help, too many for writing down but watching an expert will help alot.
6.Be patient it is'nt called the art of flytying for nothing but with time and practice it will become easy.
Good luck if I can help with anything drop me A P.M
Best wishes Aaron.