The first job of the day is to secure a big enough area for your tent. If you have a small one-man or two-man tent you won't have a problem, but anything bigger can be a bit of a squeeze. The stewards are under orders to get as many people and tents on to the fields as possible. If you have a large tent, that means "ignoring" their orders and giving yourself as much room as possible. This may sound greedy, but read the fire regulations. A large gap between tents is required.
Because the fields are used as, erm, fields there are often welcome mats to be cleared (or avoided), courtesy of the cows that normally populate the area. Crap clearing isn't always possible, but bear in mind where the brown stuff is when you lay down your tent. Strong groundsheets are an advantage!
Pitching is often a race against the neighbours - especially if space is tight! Avoid peak times for arriving (Thursday afternoon and early on Friday) and this is easier. It helps to be camping with a group of friends. More on that later.
If you are used to campsite camping, bear in mind that the fields at Cropredy at large and open. If it's windy there's nothing to provide a windbreak. You'll be away from the tent for long periods of time, too, so make sure you use all the guys and they are staked out and tight. You don't want to come back to find your weekend bedroom has been blown into the nearest hedge!
Having said that, Cropredy is a very friendly festival. If you spot a problem with a neighbour's tent try your best to remedy it. Hopefully, your neighbours would do the same for you.