Sports memorabilia may attract a different crowd from those who frequent stamp, coin or antique auctions.
But the same rules apply if you're looking to purchase with the hope of selling for a profit in the future.
Buy the best you can afford.
The more you spend, the rarer and more desirable a piece you'll end up with - if you do it right.
It's these most coveted items of sports memorabilia that have historically shown the greatest price appreciation.
And there's a further reason why you should be looking to the top end of the market if you can:
It has remained buoyant during the world's recent economic woes.
Something that sadly cannot be said for the middle and lower tiers.
That's because money is still coming in for the finest pieces - those attached to the greatest names and moments from sporting history.
But you don't have to just take my word for it.
UK-based sports memorabilia auctioneer Graham Budd put it well to CNBC earlier this month.
"Wealthy people have still got money, and in this day and age where they are getting nothing in their bank, they are looking for alternative ways to spend", he said.
Graham said much the same in our fascinating interview with him last year.
A similar thing is occurring in the US.
Reeves Wiedeman's May 6 article in the New Yorker revealed how sports memorabilia is gaining increasing popularity among investors in America, especially now that a decade of gains for gold have come to an end.
But how should you decide which piece or pieces to diversify into?
Graham Budd again:
"The things that sell the best and are worth the most are items that absolutely identify success on the sporting field."
That's why a US hockey jersey from Lake Placid's Miracle on Ice made $657,250 in February.
Muhammad Ali's fight-worn gloves achieved $386,000 last year.
And the finest Babe Ruth signed baseball has soared 16% per annum in value since 2004.
And if you want a slice of the action, here are three pieces from our stock and PFC Auctions' current sale that superbly meet Graham's definition.
I hope you enjoy this week's newsletter, and thanks for reading.