1. Set a campaign for website clicks. 
2. Use Facebook Pixel integration. Read more about how you can benefit from using it here. 
3. Pick the correct device type (e.g. iPhones only for your iPhone experiment). 
4. Don't make your targeting too broad - you will have a lot of Dropped visitors.
5. Don't make your targeting too narrow - you might get a really small amount of visitors per day if you have a daily cap. 
6. Don't set a daily cap that is less than $200. 
7. Don't add Audience Network to your placement - you might get 'wrong devices' in your experiment. 
8. Don't make your ad banner look similar to just 1 variation to avoid the biased visitor's decision to install. 
9. You might get a lot of Dropped visitors if you have already been using this ad banner for a long time. 
10. Add the store button to your ad banner. 
11. SEARCH PAGE - make your ad banner generic (not revealing any of the apps that are there on the Search page). 
12. SEARCH PAGE - make your ad text generic (e.g. Try out top 10 puzzle games), prepare your visitors to 'the list of apps' on your experimental page