List the name of the owner and the name of the business (Ralph C. Jones, individually and doing business as [d.b.a.] Jones's Texaco). But never just assume that the name of the business is really the same as the name of the owner. For all you know, Jim's Garage may be owned by Pablo Garcia Motors, Inc. (On suing a corporation, see below.) If you get a judgment against Jim's Garage and there is no Jim, it will be worthless unless you take steps to have the judgment changed to reflect the correct name. This can take extra time and trouble. Far better to be sure you sue the right person in the first place.
A few states have liberalized their rules and do not penalize plaintiffs who incorrectly state the business defendant's name. New York allows a plaintiff to sue a defendant under any name used in conducting business if it is impossible to find out the defendant's true name. California allows a plaintiff to correct a defendant's name at the time of the hearing and, in some cases, after judgment, if the defendant is a business person using a fictitious name.