Set your budget before you set foot in the room

Auction fever is real, and it costs money. The single most useful thing you can do before a sale is decide what you can spend in total — not per lot, and not on the hammer price alone. Write that figure down. Then divide it into what you are willing to pay for each coin you are chasing, and treat those numbers as ceilings rather than targets.

It helps to work backwards. If you have £400 to spend and the buyer's premium is 20 per cent plus VAT on that premium, a £300 hammer price actually costs you £372 once you have added the £60 premium and £12 VAT. That leaves very little for postage and insurance. Suddenly your £400 budget is a £260–£270 hammer limit. Do this arithmetic for every lot on your shortlist before the sale begins, and you will avoid the sinking feeling that comes with a win you cannot really afford.

Understand the premium, the extras and the small print

The buyer's premium is the auction house's fee, charged on top of the price you bid, and in the UK it commonly sits somewhere between 17.5 and 25 per cent. VAT is then charged on that premium, which adds another 20 per cent of the fee. On lower-value lots, some houses charge a minimum premium, so a £40 win can carry a surprisingly chunky charge.

• Premium and VAT: confirm the current rates in the sale's terms, as they change.
• Online bidding surcharges: bidding through a third-party platform often adds 3–6 per cent, on top of everything else.
• VAT on the hammer: certain lots, particularly those consigned from outside the UK under specific arrangements, attract VAT on the hammer price as well.
• Postage, packing and insurance: easily £10–£25 for a single coin, more for multiple lots or high values.
• Payment surcharges: some houses pass on card fees, so bank transfer is often cheaper.

Add it all up and a 20 per cent premium can become a 30 per cent real-world cost. Budget for the out-the-door price, not the headline price.

Read the lot description like a cataloguer

Catalogue descriptions are written to be accurate but not always generous. Learn the vocabulary. "Surface marks" means scratches or hairlines. "Cleaned" or "brightly cleaned" means the original surfaces have been stripped, which affects both eye appeal and value. "Traces of mounting" suggests a coin that once sat in jewellery. "Edge nick", "flan flaw", "weakly struck" and "die clash" all point to imperfections you should price in rather than hope to discover later.

Grading itself is an opinion, not a fact. A British catalogue's "good extremely fine" may be another dealer's "extremely fine", and there is no universal referee. Where images are provided, remember that studio lighting flatters toning and hides hairlines. If a lot matters to you and the photographs are thin, email the auction house and ask for additional images of the obverse, reverse and edge in raking light. Reputable houses will oblige.

Finally, check the conditions of sale. Most numismatic lots are sold "as seen" with no right of return, which makes your pre-sale homework the only real protection you have.

Inspect in person whenever you can

Viewing days exist for a reason. If you can attend, go — and go prepared. Take a 10x loupe, a small torch, cotton gloves if the house permits handling, and a notebook with your budget and a list of reference points. Compare the coin in front of you with the image in the catalogue and with coins you know well.

• Weight and diameter: a portable scale and callipers will quickly expose a cast counterfeit or a clipped hammered coin.
• Surfaces: tilt the coin under the light to reveal hairlines, tooling, smoothing and artificial toning.
• Edge: check for nicks, repairs, mounting marks or a milled edge where a plain one is expected.
• Colour: bronze and copper should not look suspiciously pink or orange, which can indicate stripping or recolouring.

If you cannot attend, consider asking a trusted fellow collector who is going to view on your behalf. A second pair of eyes is worth far more than a last-minute impulse bid.

Bid deliberately, not emotionally

Decide your method before the sale: in the room, by telephone, by commission bid, or online. A commission bid is simply an instruction to bid up to a maximum on your behalf, and it is the calmest option — provided you leave your genuine maximum, since the auctioneer will only go as high as needed to beat other bidders. Do not leave a round number that mirrors the estimate; it can invite a tie. Remember that bid increments step up in bands, so the final price may jump beyond your ceiling.

In a live sale, watch the bidding and know when to stop. Never bid against yourself, and resist the pull of a rival who is clearly determined. There will always be another coin.

After the hammer: paperwork, postage and peace of mind

Pay within the stated deadline, arrange collection or insured delivery promptly, and keep the invoice, the catalogue description and any correspondence together with the coin. That paperwork is provenance, and it will help if you ever sell or need to insure the piece.

When the parcel arrives, unpack it carefully, check the coin against the description straight away, and raise any discrepancy in writing within the house's stated window. Then store it properly — acid-free flips, a dry cabinet, consistent temperature — and record what you paid. Sound records turn a collection into something you can genuinely enjoy and, one day, pass on with confidence.