If your backyard does not have a covered deck or patio, consider renting or buying a party tent. Nothing ruins an outdoor party like rain. And a tent means that all the time, work, and money won't suffer because of a rain shower.
If your outdoor party takes place at night, be sure to have plenty of lighting, so your guests don't stumble in the dark looking for their food or drinks. You can buy or rent lighting (see our affiliated Light Kings website), or hit the garden centre for some flaming lanterns.
A party's host should never "disappear" from the party for any length of time. Do your food "prep" beforehand, so the most you'll have to do during your party is pull items from the fridge. Try preparing grilled foods that are quick, like steaks or hamburgers. This way you'll enjoy your own party as much as your guests do.
To keep down the annoyance of mosquitos and bugs, you can use citronella candles or tiki torches, and electronic bug zappers. You can also have cans of mosquito repellent available for you and your guests.