So you have narrowed your choices and you have found a local rental company. Next make sure the company's rules and requirements are agreeable to you before you sign a contract.
Is this a reputable company?
Do you know the policies and fees like security deposits and cancellation costs?
Is the contract clear on rental and mileage rates, fees for preparation, cleaning, reserving, sanitation, etc?
Know who pays for what if there is a mechanical failure, including your own out of pocket expenses.
Will the rental agency show you the ropes, like how to light the stove, or how to back up successfully?
Make a reservation early for the kind of RV you want. And you can shop pricing as the rental rates can vary significantly, and even negotiating is accepted in many places. Senior citizens can get discounts, as can some auto club members.
You will need a credit card, some proof of age, as some agencies have required minimums, and a valid driver's license. You will most likely need to bring your linens but the extras, like kitchen pots and pans might be included in a housekeeping add-on.
Check with your insurance agency as to how much coverage you will need, if any. This can be an expensive extra, so make sure it is worthwhile.