You need to start right away! If I remember correctly, you need to submit an application to the Registrar of Marriages of the area where you reside (usually the Sub-Registrar of properties also functions as this, could be different in your state) now. He puts a notice on the office notice board calling for objections, if any, in his office as also in the office where the bride/groom resides. He gives about 15 days time for objections, but in any case he cannot, I think, allow/cerify the marriage before 30 days of application.
You require 3 witnesses for the event who know the groom or the bride and probably need to vouch that they do not know any reason why the two you should not marry.
Just be aware that if you are part of a Hindu Undivided Family, the HUF is deemed to have ended when you cross this line! It may not mean much if you are not expecting a huge inheritance! If not, bettter consult a lawyer!
Rest of the stuff about getting H4 is the usual, marriage certificate, photos blah blah...
Best of Luck
H
