To get it started:
For me it was pretty simple. There was this spa on off a PA route I would drive by all the time. I noticed the spa and became ever more curious about it. One day, I got up the courage to stop there. I thought I could use my CC, but (luckily) the Mamasan told me I needed to have cash for the HF and a tip (back then, the HF was $50 and she suggested a tip of $30). So I drove to an ATM and got the cash, went back and paid the HF.
I had no idea what to really expect, except a massage. But just walking into the spa required some amount of courage and it felt like I was walking through the Looking Glass (which, in hindsight, I was). After about 40 minutes of regular massage, the girl started doing some ST and had me turn over. Then she gently grasped my dick and started giving me a HE. I almost protested (because it scared the shit out of me), but just relaxed and ended up rolling with it. I gave her the suggested tip and she seemed happy. After that, I was hooked.
For the first 2-3 years, I only went once a month to the same spa. But eventually I noticed and tried other spas in the area. The menu was largely the same, but over time some girls starting taking off their tops and offering the occasional BJ. Looking back, there were some girls I probably could have gotten more from (and were signaling me to that affect), but I was still too hesitant and inexperienced go any further. It was like this until I had one girl walk in with crotchless underwear, so there was no beating around the bush there. I started fingering her and she started moaning, took off her top and offered me FS (with apparently no up-front tip). However, I did not take her up on it then because I was just not mentally prepared to take that step yet. If fact, it was another 4 years before I had my first FS experience (though I did have other offers along the way). So the whole thing was a very gradual process. Also, around 2008 or so, I joined Spahunters and started reading about what others had experienced, which bolstered my own confidence and readiness to go further.
After I made the leap to FS (at Aries Spa), my frequency of visits increased (from once a month, to 2X a month, to once a week, and now its between 1-2 visits per week). I also branched out to coaxing girls outside their spa for outings, befriending girls at nail salons, and finally to SBs on SA.
If I had a "coach" (or muse), it was probably an ATF of mine who was the first girl I got outside of her spa. She was pretty wild and got me to do a lot of thing outside my boundaries (at that time). Being with her was a real awakening for me, increased my confidence and motivated me to try new things. She was also the one who got me using WeChat and KakaoTalk, which are two of the most important tools of the trade. I also started corresponding with other mongers.
So, overall a very gradual process that has spanned over 20 years now.