You only turn 21 once, so make it memorable. It's the perfect excuse to throw a really big party – the last time you'll probably do anything this big until you get married, or turn 40. A scary thought. So if you're [planning a 21st birthday party and aren't quite sure where to start, start with a really good theme. Here's why - Firstly, if you're partying at home or renting a space, it gives you the chance to set the scene with all the right match decorations and accessories. Secondly, a theme gets all your guests involved because they feel obliged to follow the theme dress code. Passive aggression at its most effective. Lastly, dressing up in funny costumes is just funny. Full stop.

SOMETHING A BIT MORE CIVILISED?

Not every 21st party theme has to be wild, silly or involve excessive debauchery. You can maintain a classy vibe by choosing a low key dressing up theme that's more elegant than X-rated. Invite everyone to come dressed up in black and white, for example. Or pick the kind of theme that's going to make everyone look quite hot (you, most importantly) ‘Hollywood Glamour' is always a good one.

MASQUERADE

Masks are quite a fun way of getting dressed up for your 21st celebration without really dressing up. You can go all out with a proper masquerade ball theme and encourage friends to wear the proper Venetian-style masks, or if you're one of those arty types, make your own? Otherwise you can always settle for a budget cardboard version instead. And self obsessed narcissists, can get a set of masks personalized with a photograph, so everyone looks like you for the night? Lucky them.

WEEKEND AWAY

Book a holiday cottage or caravan for you and a select number of your best mates if the idea of a big rave-style event doesn't appeal. What could be better than heading off for a birthday adventure with your besties, a big stash of booze and some great food?

HORROR THEME

It's the party theme you either love or hate. But like it or loathe it, horror can be a winning fancy dress theme that's not just for Halloween. It's a safe bet for any kind of adult costume party - including a 21st – as there's no shortage of gory dress up options. Go general blood, guts, death etc as a party theme or narrow it down to horror film genres or characters – think serial killers, ghosts, possessed children with axes etc. Nice bloody, flesh curdling, intestine splurging fun for your big day.

CASINO

The casino theme often pops up as a popular idea for a 21st. You can hire all the gear easily and have it delivered to your venue. It's a fun way to practice being rich (the pressure is on now that you 21, by the way) and gives you and your guests the perfect excuse to turn up the glamour. Insist on a high-chic ‘Casino' dress code or dress up as your favourite poker playing film character.

21ST BIRTHDAY PARTY GUIDE