The day and Time Can Matter
For one thing, the time and day can factor into how much you are going to pay for the limo in your city. It's not a rule that is carved in stone, but some limo services will allow for a discount on odd days or hours. For instance, Friday and Saturday nights will be prime time.
Check With Them First
Another thing that you will want to check on, is what you are going to be drinking in the back. If you and your friends are planning on bringing your own booze, you should check with the limo service in your area to make sure that it is OK.
It's Basic Common Sense
Most of the time they don't allow for this, or they might allow it for some type of fee arrangement. Think about it for a moment. You certainly wouldn't think of walking into your local tavern holding your own bottle of liquor to drink.
Be Nice to Your Fellow Humans
Also, make sure that you and your friends are on your best behavior. Remember that it is not your own private limo and your driver has a modus operandi for dealing with out of control or belligerent passengers, so you can find yourself dumped on the side of the road if you or one of your friends really gets out of line.
Is it Big Enough for the Ladies - Size Does Matter
Take the time to discuss with the limo service the number of people that will be in your party. They in turn can then make some recommendations regarding the size of vehicle that you need. Remember that you and your friend may and up meeting some loose American babes and having group sex in the back, so you may need a larger limo then you realize.