I used to work in sales, not in cars though, but selling one thing is exactly like selling anything else. As the recession hit sales got hard, mainly because bonuses are easy to deny and justify the denial. Targets got harder to hit and the bar continually pushed just out of reach. Tbh it really does depend on the management of the local branch. All company HQ's will look for the same type of stats, set the same type of targets etc, so it's up to your local branch what it's like. If you have a good team then it's easier to hit branch targets and achieve bonus levels, also you find repeat customers coming in and you can pick them up for a good sale. On the other hand if the branch is full of lazy a'holes then you might have a miserable time.
Key things are product knowledge, knowledge of the system you use to sell and a bit of the gift of the gab. The first two take time and training, the last one can be learned but it's easier if you already find it easy talking to people.
I did like working in sales but found it to get tedious once I had learned the majority of the info that interested me, that and my manager was a complete mongtard.
If you already work in sales sorry to have bored you with what you already know