I've read the rule book so I know about minimum cultivation and what sort of slackness will get me kicked out. They also have a well-stocked shop for fertiliser etc.
Maximum height of fruit trees?
Can I grow raspberries? Any banned plants?
Water access.
Is there a shed/where can I get a shed?
Is there a rotavator I can hire?
Are there any communal tools?
Is it too late to order potatoes?
What grows well here? (dodgy London clay if my backgarden a mile away is anything to go by)
Can I have a pond?
Anything else?
Sorry, I never got an alert for your reply.
That all looks good! I'd add -
Any pests and diseases that are an issue on the site? (some things like onion white rot can last in the soil for years)
Do people sometimes club together to arrange bulk deliveries of stuff like compost/manure/woodchip?
Prevailing wind direction, does your bit of the site ever get really waterlogged or flood?
Are you allowed to have bonfires, if the rulebook didn't say?
Do you need to remove all rubbish yourself or do they have a bin or anything there? (May or may not be relevant depending on what state your plot has been left in)
Water, as
Idaho says - and I'd also check whether it's drinkable or if you need to bring your own.
If it's not a massive site they might have their own whatsapp group or something.
Presumably you're getting a plot that someone else was using before and probably didn't do anything with for a while before they gave it up. I'd bring some thick gloves and maybe hand tools (or ask to borrow a spade or something when you're there), so you can pull back whatever's growing in a few spots and have a poke about in underneath, just to check there's actual usable soil and it isn't all a midden or layers of disintegrating old carpet underneath the weeds.
Lots of people find the no-dig method easier than rotavating etc. Charles Dowding is a big proponent - lots of info on
his website. If you're on clay I would "broadfork" (you don't need an actual broadfork, a regular garden fork will do) the soil first before covering it if you decide to go no-dig. Just push the fork in as far as it will go, rock/lever the handle backwards a bit but not enough to lift lumps of soil, return it to the position it was in and then pull the fork out. You aren't trying to dig or turn the soil, just making some space for better aeration and worms etc to move between the soil that's there now and the organic matter you'll be adding on top. A youtube video of someone using an actual broadfork will probably explain the motion better than I'm describing it.
Bring a tape measure. Try and take all the measurements you'll need to draw out a decent plan of everything that's there now, even if you don't plan on keeping all of it. And take lot of photos!