I started out with an agency back in the mid 90's. They advertised in the phone book and newpapers. After that, went indy and would use phone chat rooms. Mostly Lava Life. Also, had a couple taxi drivers and a few friends that would call sometimes with referrals. Had a lot of regulars and referral from regulars.
Outcalls were a pain. Iif you had trouble locating a place you had to find a payphone, hope you got it right that time, and if not find another payphone, etc. And you had to count on PEOPLE to give you directions. And let me tell you, a lot of people were/are really terrible at giving directions....
It was grand day when I got that first, great big. Motorola flip phone
Right before leaving the biz, it was Craigslist. Although, that was still fairly new and pretty high tech at the time (first time for pics and email appointments), lol.