1) You must write in excellent English.
2) The reviews must be related to the App
3) The ratings must be between 4 and 5 stars
4) You should add 6-10 new reviews per day till you end up to 75 reviews
5) They must be written on the US App Store
6) There is Free and Paid version of the app and reviews should be split (free 50,Paid 25)
7) We need experienced resources who know how to provide such services safely without apple banning apps from app store