Get several quotes from different party rental companies if you can, but be sure you're comparing apples with apples. Some quotes may include set-up and breakdown fees; some may not. Be suspicious of any quote that seems too low for what you require.
A large party rental company may be able to offer the services of a party assistant as well as the equipment and other items you need. Don't hesitate to enquire. If your event is particularly large or complex, an assistant might be worth their weight in gold.
If your event is a large one, you'll need to arrange a contract with your party rental supplier. They can certainly provide one. Be sure to read the fine print, however, be very specific about all the service provided, and make sure you'll get all the quantities you need.
