Invitations make the event much more personal and also lets your guests know when, where and why the party is being held. Many people have very active summer schedules, the more advanced notice you give the better. If you are thinking of having an event outside of your own property, it is a good idea to reserve any public park, or beach space now. By reserving these spaces now, you allow time to get any social permits you may need. It is also a good time to dust off the grill.
Winter can sometimes do damage to a grill kept outside.
Make sure the grill is running safely and effectively. It is also time to check the propane tank if it is a gas grill. Nothing is more of a party disappointment than running out of propane half way through cooking the steaks. Don't let the bugs spoil your party. Stock up on citrus candles, and bug spray.