1. Get to know your aircraft so well that you don't need a checklist for the walk around.
2. If you do the walk around and have allowed yourself to be interrupted, start again.
3. SOPs are there for a reason, they have been thought out over a cuppa in a nice and warm office without any stress or haste. Develop your own (however simple) and stick to them. To deviate from them under stress usually sets you up nicely for a deng.
4. Read all the accident reports you can lay your hands on. Read them AND realise that all of those that came to grief were humans, like us. None of them thought they were going to have an accident or set off from home with the intention to have one.
5. Learn from 4 that most accidents are the result of a cascade of events going wrong. Be critical of your own functioning, in all aspects and try to identify when you are getting wrapped up in one of these cascades.
6. Use checklists to your heart's content but use short mnemonics for take-off, landing and any other critical phase of your flying, to identify and check those things which need to be sorted in order not to kill or hurt yourself.
FD