Mostly I try to establish a secure perimeter right off the bat. I usually do that by setting pit and spring-loaded traps out, covering and disguising them in a few different ways.
1) Have your landing page match your ad.
2) Make the action you want to happen obvious for the user
3) keep the customer's mindset in mind.
4) what are you solving for the customer. Show how you'll solve it.
5) Tits.