When we want to buy something we normally go straight to the supermarket, the high street, or visit our favourite online retailers.
Yet secondhand items can be as good as new, but far cheaper, because they don't have the shop's mark-up.
Here are some things you might not have thought to buy secondhand, but it's definitely worth considering.
I’ve included delivery in all prices.
I'm sure most people think of brand new, fresh out-of-the-cellophane technology when they think of mobile phones and iPhones in particular.
But you could pay a fraction of the price if you buy a used, especially slightly older, model.
The cheapest unlocked, second-hand iPhone 4S in "very good condition" that I found at the time of writing cost £360, with the seller "open to sensible offers".
The iPhone 4 and previous versions are cheaper still.
Even if you want the latest model – the iPhone 5 – a new, unlocked 16GB version costs £510 at the time of writing with the cheapest, highly-rated seller – ValueBasket.com – although prices change quite quickly.
At the same time, I saw an identical second-hand phone go on eBay for less than £400, unused and still in its packaging.
I buy re-filled printer cartridges for my excellent Brother MFC printer.
These cartridges are already recycled, but buy recycled and unused second-hand through Amazon and you can buy packs of 20 for 56p per cartridge.
This compares to around £9 per cartridge when new. Even if refills are less efficient, this price makes it worth it.
I've also seen impressive, heavy-duty photocopiers going for a fraction of the new price, because offices are upgrading.
Car parts & accessories
Looking at such small items as wheel nuts, I could see several types being resold for around 10 per cent less than buying new.
A used Citroen C5 heater blower resistor went for just £4. To buy this new, you'd pay many times more.
Upgrade your speakers to Fusion 6x9 3-way speakers and you could have paid just £22 for unused and unwrapped second-hand ones, or £12 if you could collect in person. New, they cost around £40.
Buying tyres is a tricky one.
The UK’s leading tyre safety organisation Tyresafe said: "You have to ask yourself a question: if someone removed these from a car already, there must be a real good reason for them doing so."
According to Tyresafe, more than one-third of part-worn tyres have serious forms of damage or non-compliance with the law.
Problems might be hidden even if they look fine on the outside.
A small bird cage was going for only £1, collection only. Similar cages cost around £10 to £20 when new.
Secondhand feed such as mixed seed for garden birds can cost just 52p per 100g including delivery.
This is roughly half the price of the cheapest comparable new products I found.
Food and drink
I don't think anyone's going to do their grocery shopping on eBay, but you could search for restaurant vouchers.
A £25 Pizza Express voucher recently went for £16.25.
I also watched large unopened bottles of spirits go for between £4 and £5. (I only watched!)
A few tips
Don't just check eBay. Look to Freecycle, place an advert on Gumtree and check out websites such as preloved.co.uk.
Check you'll get the required proof for any warranties.
I looked at some xenon HID car lightbulb kits and found that the cheapest shop-around prices for second-hand kits were sometimes the same as for new ones.
Some secondhand Whittard of Chelsea hot chocolate even sold at a premium, so look at both new and secondhand prices.