So you've decided to have that special event in your backyard rather than renting a hall or a restaurant. Good for you, you'll probably save some money! Now comes the tricky / fun part - planning the day. Here is a checklist of common items for your convenience. Lets assume this is an adult birthday party and you are expecting 40 guests. I won't get into all the food and beverage stuff, but here is a checklist of party items.
tent (optional but encouraged)
seating (round tables, folding chairs)... cocktail tables are a nice touch too.
long tables for food, gifts, etc
lighting depending on what time of day
table covers (linen or plastic throwaways)
trash barrels / trash bags
coolers w/ ice
mixers / cut fruit for drinks
cutlery / plates / napkins
entertainment (music, speakers and yard games)
bathrooms (if you don't want people in your home, you can rent basic or luxury bathrooms dropped right in your yard)
I'm sure I've forgotten some things, but these are the most commonly asked for / forgotten about items.
Now, head over to BackyardTent.com and get quotes from local rental businesses.