A new number plate arrives next week, and it could save you thousands on your next motor.Tuesday marks the start of September and the introduction of the new '76' age identifier, succeeding the '26' plates fitted to models registered after March 1.For car dealers, it is one of the most important months of the calendar. And for buyers, it can be one of the best times to bag a bargain.It's a time when manufacturers roll out some of their biggest promotional offers, finance deals and incentives of the year to capitalise on increased showroom footfall.And dealers are typically given more wiggle room to extend discounts if it means luring a customer away from a rival showroom just down the road.But with around 50 brands competing for your cash and a bewildering range of deals, knowing where the biggest savings can be found isn't always easy.Pat Hoy from Insider Car Deals has spent more than two decades analysing new-car prices. His team of mystery shoppers also haggle in showrooms nationwide, uncovering exactly how much buyers can negotiate off sticker prices to reveal where the real bargains are hiding.We've enlisted his expertise and behind-the-scenes industry data to bring you a one-stop guide to getting the best deal on a 76-plate car... Tuesday marks the start of September and the arrival of the '76' plate age identifier. For motorists, this is one of the best times to bag a new-car bargain. Here's our ultimate guide to doing just that Hoy's first piece of advice to motorists actively in the market for a new car is not to hang around.'Salespeople are keener to do deals, especially early on, when they're chasing targets and want to report a bumper September,' he says.'Later, if manufacturers are happy with the volumes they've achieved, that keenness can fade.'He explains that brands use different approaches to provide discounts, though many are leaning heavily on finance contributions to tie drivers into agreements that will typically see them return as customers in three to four years' time.'Cupra weighs its discounts towards PCP deals, with more than £5,000 of deposit contribution available across the range, plus £1,533 from dealers. Hyundai leans the other way: an average dealer discount of £3,298 compared with a finance contribution of £1,514.'But he warns that big discounts are not everything and that drivers need to crunch the numbers, especially if they are financing vehicles.'PCP APRs can have a big impact on the total amount you pay. The market average is 5.4 per cent, yet BMW and Skoda offer 2.9 per cent on selected models, while Vauxhall Astra buyers are being offered big discounts but APRs of 10.9 per cent.'It means some of the best deals are on cars that are not subject to huge price cuts but are available with a lower rate of borrowing.Hoy also says that the 'very best offer' a car salesperson will typically offer a customer is rarely the very lowest they can go.On average, his mystery shoppers secure extra savings worth £1,469 more than buyers who simply accept the initial 'very best offer'.For premium brands, this 'discount gap' extends to £3,137.