Are you planning a big shindig like an outdoor wedding reception? Your list of items to prepare for the reception is likely very long, so having a party rental company cover most, if not all of the items is easiest. But when you go through the party rental catalog, don't just choose the big stuff and be done with it. Remember the accessories, such as the following items, that will make your event more comfortable for your guests.
If the party will be outside on a lawn and will be relatively formal (or at least fashionable), having a hard floor set down on the lawn is essential if you want people to be able to wear high heels. But don't forget a walkway or stepping stones. Unless the temporary flooring is going to be placed right up against your patio, your guests will need some way of getting to the temporary floor without having their heels sink into the lawn, and without getting mud all over the hems of their clothing if it had rained earlier.
You know about heat lamps for chilly evenings, but you may want to have some fans around even when it's not that warm out. Fans help circulate the hotter air from the heat lamps, making the party area's temperature seem more balanced. On warmer nights, the fans help combat humidity and the unpleasant closeness it can bring. They can also make it harder for flies to buzz around your guests.
Non-Food Party Favors
These might not be a necessary thing, but they'll make your party memorable in a good way. If you have guests with varied dietary restrictions due to allergies, religious needs, and more, even something as simple as chocolate drops can be controversial (the caffeine and theobromine in chocolate can aggravate a couple of medical conditions, like interstitial cystitis). Avoid that whole problem and have a few non-edible party favors for your guests. Don't distribute the favors based on who you think has what condition -- place little bowls of the favors on each table and let occupants choose what they'd like to take home.
Start planning now, partly because of the time needed to arrange for everything, but also so you'll have time to find exactly what you want without feeling rushed. Each party rental company will have its own catalog, so reach out to one like City Rentals and have fun seeing what's available.