Take down any photos, mirrors and ornaments and store them somewhere safe.
Move furniture. If you have the storage space, you should completely clear the room of furniture. If that’s not possible, just move it to the centre of the room. Your painter should bring protective sheets to the job but it’s a good idea to check on this with them before they arrive.
It’s worth removing curtains and blinds to protect them from paint splatters. This may even be a good opportunity for you to give them a thorough scrub and clean.
If you’re preparing the walls yourself, make sure you finish the day before so the painter can start right away.
Run the vacuum cleaner over the carpet so there’s no dust between the carpet and the baseboards. The last thing you want is a gust of air blowing the dust onto the new paint before it dries.
It may sound obvious but make sure you have enough paint. Be sure you know “how much paint I need for a room”. There’s nothing more disruptive than having to run to the paint store halfway through decorating.