Dealerships are pressured to sell during certain periods, so catching them during these times will give you maximum negotiation leverage. Not only will you land a better deal, but it will be a much easier negotiation process.
I'm going to start from the best time of year to purchase, and take you all the way through to the best time of day to purchase.
Not everyone has the luxury of choosing exactly when to buy a new car. If your current vehicle gets totaled or stolen, you pretty much have to replace it right away. But for those who can wait, there are a few times during each year that offer the best negotiation opportunities.
Most insiders agree the best time of year to purchase is the week between Christmas and New Year. Most people aren't shopping for cars during this time, and every dealer is striving to meet end-of-year sales goals. This is especially a good time to purchase a leftover model. Manufacturers tend to offer large rebates just before the end of the year to clear out all remaining models.
If you're considering the most recent models, January and February are good months to buy (as long as incentives don't drop much from end of year). Sales are usually slow and you'll take advantage of the fact that many manufacturers raise prices as the year progresses.
Certain holidays offer good buying opportunities since manufacturers tend to offer special incentives. President's Day is one of the best holidays to shop for a new car. It occurs during the 3rd Monday of February, when sales are slow and inventory should be plentiful. Other good holidays are 4th of July, Memorial Day, and Thanksgiving weekend.
All dealerships work in monthly cycles. Sales, commissions, and bonuses get calculated on the last day of each month.
Many high-volume dealerships make most of their profit through manufacturer bonuses when they hit certain sales goals. If the dealer hasn't sold enough cars to qualify for these bonuses, the pressure to sell near the end of the month can be tremendous.
You should start negotiating during the last 4 or 5 business days of the month. You may not get the price you want right away, but as the last day of the month approaches, it's common to hear back from dealers agreeing to a deal as long as you purchase that day.
The best time during the week to purchase a new car is on the slowest days. This would be Monday thru Thursday.
When there isn't much foot traffic in the dealership, the pressure to sell increases and not only will you be given more personal treatment, but you'll likely land a better deal. It's even better if the weather is horrible, such as when it's pouring rain - you can bet there aren't many people shopping for cars that day.
Whatever you do, don't try to negotiate a deal on the weekend. This is when everybody else is out shopping and the pressure to sell isn't as great.
The best time of day to negotiate is late morning thru late afternoon. Again, this is the slowest time for a dealership (see a pattern here?).
You don't want to start contacting dealers first thing in the morning, because that shows you can't wait to buy the car. You also don't want to contact dealers after 5PM, when other car shoppers start showing up after work.
Contacting them an hour or two before closing is also another good time to start your negotiations. Most employees are eager to go home and landing a deal at the end of the day is a nice bonus - even if they don't make much profit.