first of all you have to go for qatar I/D. and then you have to prepare documents like married certificate,your wife's child's birth certificates,(translated in arabic)
attested by your country qatar embassy and foreign affirs,and then your country embassy here and foreign affairs,letter from your company saying your current salary,position,your visa position should be higher.and then passport copies of you,your wife & child.flat details and elctricity bills of where you are going to live.there is a form to be fiilld in arabic which you can get done by places where arabic translation and paper works doing. and then apply.if there is anything required more than this, Immegation officer will tell you before you submit, when you go to get his signature.