First you should consider checking the pool if it’s clean, swim ready and safe for the party. If not prepare the pool first also make sure that all pool chemicals are stored away from pool.
Store and place all plastic and paper utensils to use for eating and drinking. You should avoid using glass items near swimming pool since it can cause accidents if glass brakes on the floor, it can all create problem to you pool equipment if glass pieces fall into the swimming pool.
Arrange chair and table at safe distance from the swimming pool. Also place trash cans little far from party area so that bees, flies don’t come to your party.
Arrange extra towels and swimsuits even board shorts in case your guests forget to bring those items.
To make your pool party exciting you should also consider arranging entertainment items inside pool as well as outside pool. You can get balls, rafts etc… inside the pool and music is always one of the best option for party.
And finally most important thing setup an open air kitchen to serve food to your guests. Swimming burns lots of calories so you guests will need food which is easy to prepare and can be serve quickly. Hamburgers and Hot dogs may be good choice for such season. Barbecues and pool parties go together very well, they are very easy to cook and salads are nice choice for summer season. Items which take time to prepare should be prepared earlier to the party so that you can heat it in oven and serve quickly. You can arrange any special food options according to you theme if you are planning any special theme pool party.