Should I book the desert tour in advance or on arrival?

My answer leans toward booking ahead, and the main reason is timing in the calendar. Morocco's desert season peaks in spring (March–May) and autumn (September–November), plus the Christmas and New Year week, and in those windows the good private driver-guides and the better camps genuinely sell out. I've had to turn away guests who left it to the last minute in October simply because every reliable driver I trust was already on the road. If your trip falls in peak season, lock the tour in before you fly.

Booking on arrival isn't reckless, though, and in the quieter, hotter months (high summer, or deep winter outside the holidays) it can work in your favour. There's more availability, you can sometimes negotiate a better rate face-to-face, and you keep the flexibility to change plans if the weather turns or you fall in love with a city and want to linger. Travellers on loose, open-ended itineraries often prefer to sort the desert once they're on the ground and have a feel for the country.

The real risk with arranging it on the spot isn't availability — it's quality and pressure. The desert tours sold hardest from medina shopfronts and budget hostels are often the crowded 2-day minibus dashes, and you're buying blind, with no time to vet the operator, check reviews or confirm exactly which camp you'll sleep in. I've met plenty of people who booked a 'great deal' the night before and ended up on an exhausting 2-day Merzouga run with a basic camp, simply because they had no leverage and no time to compare.

So here's how I'd play it. Peak season or anything special — a private tour, a particular luxury camp, a one-way Marrakech-to-Fes route — book in advance, full stop. Travelling in a quiet month, flexible, and watching your budget — you can arrange it on arrival, but give yourself a day or two to research rather than buying from the first tout, and never let anyone rush you into the 2-day dash. A little advance planning almost always buys you a better desert trip.