Having now been on the selling end, I can tell you that a lot of car buyers are annoying and rude without meaning to be. There are two key ways to avoid being one such customer:
1) KNOW WHAT YOU WANT.
Not just the make, model and age. For instance:
- Know what sort of condition you want the car to be in, and know what is acceptable for a used car of that age. Expect some scratches. If you want a car that looks brand new, then go to a dealer because they'll have done all the painting and replacing of parts that a private seller may have actually been advised *not* to do because it's not worth their while and isn't compromising the safety of the car.
- Know what you want to know about the car. Don't call up and ask "What can you tell me about your car?" because chances are that all the relevant information is already in the advertisement. This makes you look like you don't know what you're doing or what you're after and won't endear you to any car owner with half a brain. Keep it specific to things that weren't already given.
- Don't email or text making excuses for not being able to talk on the phone. No sensible seller will ever get back to you. If you can't talk, get someone to call on your behalf. The first bit of advice to anyone selling a car online is always to make contact in person before any transaction takes place.
- Know how much cars of that type and age are being advertised for, and know how much you want to pay. DO NOT call up and ask the seller "What's your final offer?", because that is the stupidest question you could ask. No seller in their right mind would give you a lower price than what they advertised. If you don't want to pay what they're asking for, then for heaven's sake, have an offer prepared and give them that. If they are happy to negotiate, they will make a counter offer. If not, they'll tell you so.
- DO NOT start trying to lower the price before you've even seen the car. This is just rude. Excuses like "It's a manual" or "It's a few years old" will just make the seller wonder why you're enquiring in the first place, if this car is so crap by your own standards.
2) COMMUNICATE UP UNTIL YOU DECIDE AND THEN EVEN AFTERWARD
There are few things worse than being left hanging. If you decide against a car, then for goodness sake call the seller and tell them as soon as you come to that decision. And try to tell them why. It can be as simple as "I like another car better", and that's OK; they just have to accept that.
On the other hand, if there is something wrong with the car, tell them before you decide for sure as it may well be something that the owner is willing to fix at no cost to you. But you know what? THIS CAN'T HAPPEN IF YOU DON'T TELL THEM. It also makes it a lot harder for them afterward because they just won't know why their car was rejected, and if it can be fixed then they can do so and maybe have it ready for the next person who is interested.
It's not hard to not irritate people. You just need to be prepared, both to know what you're doing and to communicate effectively. Ultimately you don't owe the seller anything, but it's not hard to be kind and make life easier for other people, and nothing I've listed will cause you disadvantage in any way.