Hi, I'm new to the forum also. We had a corporate catering business for many years. Currently operating a QSR concept, have done concessions, etc etc. Anyway:
Be able to accept ALL credit cards. Create a profile of all customers and include a CC# on file. Customers order and you punch in the card # and print the usual slips. You are then PAID. Upon delivery, have them sign the Merchant copy (include a tip line on there if you wish, some offices tip with cash) Input charges for ALL orders for the day first thing in the morning to make sure the damn card works. Leave a professional itemized invoice along with their copy of the charge slip in an envelope with your Logo and company phone #.
Some of these folks may request corporate billing. You will have to make the call on that one. Be prepared to wait 30-60 days for payment from a corporate office somewhere.
Look into courier services that may also do drop-off food deliveries, this will allow you to get down in wider areas. They may charge $10 - $20 per one-way drop. Pass this along somehow to the client.