Here's a simple trick I spotted just last week, one I hadn't noticed before, not in almost thirty years of bidding at offline auctions, one that could turn every auction you visit into a fabulous source of high price items that you'll pick up for pennies.

I sat there, Wednesday last week, wondering how, in just one day, and a few hours before the auction starts tomorrow, can I possibly see what's in these forty plus albums and suitcases filled with postcards, three hundred plus albums and shoes boxes packed with stamps and first day covers, and an entire shelf filled to the brim with cigarette cards and paper collectibles? How can I ever know how much to bid on almost six hundred auction lots, some of which take a minimum one hour just to flick through with no hope of perusing properly?

And where are those people who regularly bid against me at this auction, people who always spend thousands of pounds at this venue? They were nowhere to be seen on Wednesday, they arrived catalogue in hand next day just a few minutes before bidding commenced.

Maybe they got a sneak preview, a private viewing of items they'd bid for today? But no, I realise that doesn't happen here. When the answer finally dawned on me it opened my eyes to a wonderful way to bid at auction with confidence, even without viewing beforehand.

You see, you really can't view properly at auctions packed with multi-item lots and short viewing periods. Realistically, it could take months, dare I say years, to inspect every postcard, every stamp, every coin and cigarette card, every print, every book, every piece of paper for profit potential?

Over coffee, people I'd known for years confessed they wondered why I spent so long viewing items when a simple statistical formula was all they used to determine their maximum bids.

Let me emphasize this doesn't work with single lot items, like vintage dolls and teddy bears, paintings and toys trains. It only works with multi lots containing hundreds of items.

The trick is just to trust the auctioneers' estimate of how much a lot will fetch and never exceed that amount. Some bidders stop at the top of the estimate, others at the bottom, yet more buy only items that sell below estimate.

Also consider that offline prices are invariably inflated on eBay, where even common collectibles can reach way beyond catalogue value. Most offline auctioneers estimate according to offline value, they're rarely 'techies' and few are personally familiar with eBay, so whatever they think an item is worth can often be double, tripled, or more on eBay.

Tips

* You should always take a brief look at high estimate lots, people make mistakes, there could be typing and printing errors to inflate an otherwise affordable price. Like the rest of us, auctioneers have 'off days', when their estimates will be way off target. A quick check of a handful of lots will reveal how carefully today's lots were valued.

* Do not use the technique until you have experience of particular auction houses. View in advance of your first two or three sales, estimate values, check how closely estimates match actual realizations, calculate statistical accuracy for individual lots and write this in the margin alongside. Where lots typically go within ten per cent of estimate (higher or lower) add 10% to the margin. Where estimates double add 200 per cent and trust auctioneers with low percentage points over others whose estimates vary widely, and consistently, and can never be trusted.

Avril Harper is a triple eBay PowerSeller and editor of eBay Confidential and webmaster of http://www.publishingcircles.com. She has produced a free guide - 103 POWERSELLER TIPS - which you can download with other freely distributable reports and ebooks at http://www.toppco.com