ok, here are some commonsense tips from a layperson.
Make sure the buyers are genuine. Not the type that would snatch away your car while on a test drive. Be careful letting people in your home.
bayana will depend on the price of your car but Rs. 10,000 or more (in cash) sounds reasonable.
You don't give them anything with the bayana (no papers, nothing). They should arrange full payment in a day or two and bring it to you (you dont go anywhere to receive the payment).
For the rest of the money prefer Bank Pay Order. Cash is risky, what if notes are counter-fit, stolen money etc.
Pay Order should have double signature, but that is not enough. You personally take the pay order to the concerned bank and get it verified that it is a genuine Pay Order and not jali (counter-fit). Take the buyer with you if need be but get it verified at your local bank branch of the same bank.
Once you have the verified pay order, you can handover the car and documents.
The buyer will ask you to sign the Transfer letter and car sale receipt.
You will ask buyer to sign a delivery letter stating that they have received the car and documents at such and such date and time and that it is in good condition and they are fully satisfied and they will not claim anything or hold you responsible for anything afterwords.
Make sure you have family or friends with you (as witnesses).
You will also keep a copy of buyers ID card and those of all others involved in the sale/purchase, get buyers contact info (home, business address, land and mobile # etc). Plus make copies of all documents you sign.
These are just some commonsense tips. Experts can guide you more.