Truly, word of mouth is my method. The hairdresser I go to now (I know you said beautician, but obviously with service providers like this the same rule applies no matter which field they specialise in), is a total gem that my mother (of all people, as if I would trust her judgment on anything) found for me.
When it comes to this kind of stuff, I usually approach it from a 'process of elimination' standpoint - ask around (even post it on FB that I'm 'looking for a new waxer - any recommendations?') and get people's opinions... whichever salon/staff member has the least complaints about shoddy work or a bad attitude or overpriced services, I give them a go. It's a points system, add points for good things (cheap, friendly, exceptional work), and minus for the bad - points vary and are awarded on a scale basis.

...I just realised how complicated and, well, WEIRD that sounds. But it's a system that I have found works. And the few mistakes I've made, are easy to fix - I just don't go back there!!
So, word-of-mouth is your best bet to get 'em through the door, but keeping clients is about treating 'em right and making them want to come back again