I mentioned before that I took out a loan for a car last year.
The first thing I determined is what my budget would be - I was primarily looking to pay back about £300/month over 2 years, and went car shopping.
When I finally decided on a car to buy, I found I needed to up my budget, which basically meant rising the monthly payments a bit, and extending repayments over another year.
In the end I bought a VW Touran for £17k - paid around £5k in cash, and got a loan for £12k, to be paid over 3 years @ around £360/month, so that worked out fine.
What was good to see was HSBC normally offered a rate of around 85, but without any haggling, they offered me a rate of around 5.5%, which I thought kind of cool. Means I could probably have haggled for something lower, but I was just happy to get everything moved forward smoothly.