You just need conviction in your decision, as theres no legal problems.. see this post: http://bok498a.blogspot.com/2008/04/legal-position-of-bigamy-adultery-vs.html (also see two reports about a similar situation of actor Pawan Kalyan).
Bigamy(IPC 494: http://www.vakilno1.com/bareacts/IndianPenalCode/S494.htm) is only if someone can prove that u r married(example: if you are a hindu; as per Hindu Marriage Act)- so don't marry... so no proof of marriage possible....simple, keep/take no photos of any ceremony distantly similar to marriage, or create any marriage record. Just live with ur friend for life, theres a word "companion" gaining respectability in even Indian cities, anyway if u don't care a damn about society, all this is no bodies business. But be wary of IPC 493, which says that if u induce a belief of marriage in a lady, when u are only cohabiting, thats chargeable with IPC 493(http://www.indialawinfo.com/bareacts/ipc.html#_Toc496765386 ,10 years max boss, so be very sure about ur companion!, else its back to battle again, but thats no big deal for u all now, right?;)
As far as Adultery(IPC497: http://www.vakilno1.com/bareacts/IndianPenalCode/S497.htm ) goes: Only a husband can sue a suitor of his wife, if this suitor knows that this lady is married and has no expressed consent of the husband to get close to his wife!- so its funny, its saying wife can't get a husband punsished for adultery(only husband can frame his wife's suitor. not even his wife!), plus this law actually points towards threesomes!!!. So give a F&$K to the law and in-laws and get ahead if it suits you.
Basically it all boils down to your conviction and how afraid u are of society- which never helped or shielded you from harms way when you really needed that(in case u r not convinced that much about ur decision to go ahead and live with ur companion). So y give a damn about the so-called society, show them ur middle finger and walk tall and straight ahead where u wanna go.
Why I explained this in detail is that after 2-3 years most of the elders in the family are worried silly about getting boys(or girls for that matter, but we don't have to empathise with those law misusers, right?) married(to see their grand children play before the end of their days, as the popular concept in India goes). So its important to pacify those worried parents and senior citizens and show courage by taking you life into ur hands, and either decide 1) not to marry(just ensure that u are sufficiently amused and live an interesting life however it suits you- but yes, take care and use protection), 2) not rush to marry, or 3) if u find someone and are fairly confident that shes not the garden-variety-498a-girl(u can't be 1000% sure anyway, but these are the risks u have to assess and own-up) just start ur life dont wait for god to really appear before you- just understand that he has provided with just enough loop holes for u to survive and have a fulfilling life.
So the message is that live the life you want to, don't ever be limited by any restrictions either imagined/imposed by self or projected on to you by others- believe in the infinititude of human mind.... where theres a will, theres a way... period. Come on legal hassles are not Greek and Latin to u guys now, u can in fact be consultants in 498a issues, so do what u wanna do, "IMPOSSIBLE IS NOTHING"(quoting a sports company's catch phrase).
BTW, if someone wants the exact ways and means to proceed as above, I have a "template"(like the advocates have the false 498a complaint template) which can be shared in Private(but guys someone tell me how to create a password protected folder or page in the web, else I will be most probably spending all my time replying to your queries in this regard, so please tell how to password protect a webpage or folder- A word file should work, but any more intelligent solutions, so that it won't be misused much(not worried about this much, since I have stopped fretting about being morally correct and stuff like that) and that I don't get into another soup!... not that I mind it , but for now, I would like to devote 100% of my time to send the misusers packing to where they deserve to be).
I know this realisation would be a great relief and reason for reformation to many. Swarup is one walking talking example of such a guy, and he is not alone , that population is increasing(thanks to the law, we are being made stronger and invincible). I will leave you with a thought provoking and pragmatic quote "The supreme act of war is to subdue the enemy without fighting!" . So live anyway, but fight only if warranted.
Also read this post: