Christmas. ‘Tis the season to be jolly. And for some, betrothed. The wine flows on tap, and relatives are more affable than annoying (for once). Which makes for a heady combination of high spirits, actual spirits and family values – the perfect Dutch courage recipe for popping the question. (Just not the kind to tell your auntie you hated that deodorant gift set.)

December is the unofficial engagement period. Don’t believe us? Just take one look at your Facebook feed on Christmas Day – rings and hands and #blessed for days. Which is understandable – after all, committing to a lifelong mate is a landmark event: we’re supposed to propose only once, so it should be memorable.

But popping the nearest bottle is far easier than popping the question itself. It takes months of preparation, grappling with etiquette and, most importantly, the perfect ring. Especially if you’re planning on a surprise. Which is why we’ve spoken to three experts to fill you in on what you need to know before you stoop to one knee.

Preparation Makes Perfect

So you’ve found the woman (or man) of your dreams. Great. But before heading to the nearest jewellers for a rock to rival Uluru, you need to get your head round the basics.

“If you’re buying in secret, ring size is very important,” says Craig Bolton, executive director at Goldsmiths. “A ring from the jewellery box is a good indication of the size needed. But if she’s more hawkeyed, we offer a printable online ring sizer that measures the right ring finger. From there, we estimate the engagement band.” There’s still a margin for error, though – which is why Goldsmiths introduced an adjustment service to ensure a closer fit regardless.

It’s also worth learning the four Cs of diamonds – Colour, Clarity, Cut and Carat weight. Here’s a brief overview:

• Colour – A chemically pure diamond has no hue, so look out for a distinct lack of colour.
• Clarity – High-quality diamonds should be clear, so no frosting, blemishes or ingrained crystal.
• Cut – A strong diamond should boast outstanding light interaction (sparkle, to you and me).
• Carat Weight – Heavier is larger (and often better quality), but also more expensive.

But there is another ‘C’ you should consider: Cost. It helps to have an idea of budget and their taste in general too, says Bolton. As diamond bands range from £500 to the hundreds of thousands, your initial consultation won’t be all that fruitful if you haven’t done your homework.