i met my my first Dom online at another site. after talking (and doing tasks such as writing for him) via e-mails and then the phone for several months, i finally got the nerve to met him in rl. during our phone conversations he would have me masturbate for him and cum only when he gave permission. when we finally met( and after some time getting to just talk in person) he forced me to have orgasm after orgasm using a vibrator. i don't know if that even counts as BDSM, but god that man could make me cum with just his voice, before we parted ways a year or so later.

to answer the rest of your question, a good place to start is certainly by yourself with things you enjoy! it usually takes a good long time to get comfortable with someone you meet online or in rl to do these other things. but when you do, and its the right person it is well worth it