Bring a radio. This is an essential item especially if you are in an area where you cannot use a nearby car radio. Bring a trash bag to place empties into. If you keep your party area clean it is less likely that anyone will discover your secret location, plus your woodland friends will appreciate it. Now that you have gone down the checklist, there are a couple of other things to keep in mind.
Large gatherings are always fun, just make sure there is enough parking for all invited.
If not, car pool. Make sure to pick a spot where you are not going to get yourselves arrested. Many landowners do not take kindly to a bunch of people drinking and setting fires on their property. Try to avoid letting the entire town know where you are having your gathering. Too many unknown people can spoil any gathering, plus they may be a little careless and accidentally alert the authorities to your location.