If Visit Visa :

1. NOC from your company stating your job designation, salary , and the families you will sponsor.

2. Passports copies of each families as well as yours.
3. Your Qatari I.D.
4. Marriage Contract copies and Birth Certificates of your children.
5. If your NOC from the company did not mention that you have accomomdation then you also need copy of your tenancy contract under your name.
6. About the salary , it must not below QR 4,000 . PLEASE be reminded that IT ALSO DEPENDS upon the mood of who will approved your application coz mine was approved showing basic salary of QR 4,200 . The visa was approved 4 days ago . ( There is no harm in trying )
7. Application form , go to typing area in Garaffa Immigration and pay 10 riyal each application.
Good luck !