if you want to visit for short term only, u can apply for tourist visa only and it can be done through travel agencies.

if you want to visit for more than one month you can try family visit visa if you have family in qatar. the requirements are, copy of your passport, copy of document the proves your relation to your sponsor (birth certificate or marriage certificate), id copy of your sponsor, NOC from the Company of your sponsor indicating salary and other documents from your sponsor's company, filled up application form. .