This is the most important factor while selling your car in India because there are a lot of legal issues that people face generally while documenting. Generally, a common error that a lot of people make is that they delay the owner transfer, and generally the second or the third owner whosoever is buying your vehicle might go through an unforeseen accident, and ultimately the responsibility goes to its original owner on paper irrespective of whoever was driving it. So, never neglect your documentation, documentation should always be at the top priority while selling your vehicle. Whenever you are selling your vehicle always have a NOC because generally vehicle owner transfer can take one to two weeks so for that period of time you can have a stamp or a NOC that you are not responsible from that point of time towards that vehicle and you have sold to that respective person.

Always look for good options while selling your car. Generally, you can get a good price for your vehicle if you sell it to a direct customer because when you sell it to a second-hand car dealer or to someone who is a third-person knowing some other person who wants a vehicle or a few sell it directly to a car dealership. You can find different prices for your vehicle through the value that you will be getting for your vehicle depends upon your vehicle’s brand, kilometers, and the condition that it is at but if you look for a good deal you can find a difference of 20,000-30,000 as well for what you're getting offered and what you get actually if you make some efforts.

Always before selling your vehicle you should get all the service records updated by default. Keep all the service records updated if you get all the services from the authorized showroom so you should keep a log of all the service history so that the person who is buying a vehicle has a clear idea about how much the vehicle is driven at what point of time and is the service done on regular intervals or not.

Do care about the payments, never fall into the trap of some people saying to you that they'll make you a payment after the vehicle gets transferred in their name or if they try to convince you that they will transfer you money after a few days or few weeks. Always try to get all the payments done on the day, you hand over the keys to another owner because when all the documentation is done then they can run away and you can just have a disappointment and nothing more. So, always keep in mind to have clear documentation and all payments should be cleared out before handing over the keys.

Before selling your vehicle if there is some defect in your vehicle then it is your responsibility to either get it replaced or you should inform the owner about the part but do keep in mind that you never have to take any guarantee for any part of the vehicle. 

Once it is sold then it is the entire obligation of the owner who is buying that car so, you should not be obliged or be forced to be obliged to the cost of any part being broken or being replaced after you have sold your vehicle. So, if there is any part that needs to be replaced or repaired then notify the owner of the vehicle to get it replaced or else you get it replaced from your end, and before selling you should include that while selling in your cost.

From all these 5 points according to me the most important thing to look at is documentation because a lot of people fall into this trap and get a lot of problems due to not transferring the vehicle to the other owner's name. So, always keep your documentation very clear and prescribed so that you later don't get into any trouble.