Most guides to planning an event hand you a checklist. The trouble with a checklist is that it tells you what to do but not when, so you end up doing the easy things early and the hard things in a panic the week before.

This one is arranged by time instead. We've been the supplier at the far end of hundreds of these, which is a strange but genuinely useful vantage point — we turn up after every decision has been made, and we get to see which ones held up.

Twelve weeks out

Lock the date and the room, in that order

Almost everything else bends. Your guest list will change, your budget will move, and the theme you're certain about today will not survive contact with what's actually available. The date and the venue are the two things that get harder to change every week you wait.

Book the room before you plan what goes in it. People do this backwards constantly — they build a whole vision around a space they haven't confirmed, then have to dismantle it when the space falls through.

Get a real headcount range

Not a number. A range, with a floor you'd be disappointed by and a ceiling you'd be thrilled by. Every quote you ask for from here on should be against that range, because suppliers price differently at 40 people than at 120, and you want to find that out now rather than in September.

Decide what the night is actually for

One sentence, written down. A fortieth birthday where the point is that everyone finally meets each other is a different event from one where the point is dancing, even at the same budget in the same room. Almost every awkward decision later — seating, music, whether there are speeches — gets easier once you can hold it up against that sentence.

It also tells you where to spend. Which brings us to the part everyone gets backwards.

The budget, in the order that matters

Work out your total, then take a quarter of it off and put it aside. What's left is your real budget, and the quarter is what you'll spend on the things nobody puts on a plan: ice, cabs, an extra hour of venue time, the cake that didn't get collected, tips.

Then spend what's left in this order: the room, the food, the drink, and everything else. That order is dull and it is correct. Guests forgive a modest room with good food far more readily than the reverse, and no amount of decoration rescues a party where the bar ran dry at nine.

The most common mistake we see isn't overspending. It's spending evenly — a little on everything, so nothing is actually good. Pick the two things your one sentence says matter, fund those properly, and be honest that the rest is filler.

Six weeks out

Book the things that only exist once

Catering, photography, music, and anything else where there is exactly one of the good ones and someone else is also trying to book them. Saturdays in summer and December go first, sometimes six months ahead.

The best suppliers are booked by people who decided early, not by people who decided well.

Ask every supplier the same three questions

How long do you need to set up, what power do you need, and what happens if something breaks. The answers tell you more about whether someone is any good than their portfolio does. Anyone who has worked a lot of events has a clear answer to all three, because they've had all three go wrong.

Send the invitation

Six weeks is the sweet spot. Earlier and people forget; later and they've made other plans. If your event has a dress code or a theme, this is where it goes — it needs to arrive with the date, not as a follow-up nobody reads.

The week before

Walk the room, or make someone send you photos

Where the power outlets actually are. Whether the door your caterer is using is the same door your guests are using. Whether the beautiful corner you'd earmarked has a fire exit in it.

This is the highest-value hour in the entire process, and it's the one people skip most often.

Confirm arrival times in writing

Not "we'll be there in the afternoon." A time, per supplier, with a phone number attached to it. Then send the whole list to the venue, so whoever is holding the keys knows who to expect.

Decide who's in charge

Someone has to be the person suppliers call when the lift isn't working. It shouldn't be you if the event is yours — you'll be greeting people. Name someone, tell them, and tell everyone else.

The day itself

Very little of the day is in your hands by this point, which is the entire reason for the twelve weeks in front of it. What is still in your hands is smaller than you'd think and matters more than you'd expect.

Eat something. Build a buffer between setup finishing and guests arriving, because setup always runs long and a room of early arrivals watching people tape cables down sets an odd tone. And go and look at your own party at least once from the far side of the room, on purpose, while it's happening.

That last one isn't logistics advice. It's the only part of the night nobody else can do for you, and it's the part people tell us afterwards they wish they'd remembered.

If you'd like a hand with the part we're good at, tell us about your event.