Talk, ask, read, talk, talk, talk Ok you get the picture.

Honesty is key to it in my opinion, slow and simple starts which require patience, my experience is as a sub introducing a male Dom who was vanilla mostly.

Try something that works as vanilla and spice it up, then talk, then talk after a few days to make sure that nothing has come up.

Oh and before all of this my experience has shown that communication and completel honesty is vital in D/s and BDSM so I would suggest starting with what does turn you on both BDSM and Vanilla, talk about fantasys and see if you can start with what you know. Incorperate one small aspect into something that is 'comfortable' already.

Reassure and praise, overly so maybe to show that you appreciate what the person is doing. Never forget that you came in caring about each other and don't let it take over your life or put pressure on, if there is pressure then take a step back and play as you would before.

Make it clear from the start that mistakes will happen and if something goes wrong you are not going to scream the house down, blame them for hurt or anything like that. One of the worrys that I have come across is the not knowing what to do, or what if I hurt you. Have a safe word, put safeguards in place and enjoy.

I would reccomend Screw the Roses send me the Thorns - it's a great introduction and is done with humour and respect as well as passion and understanding written from both male and female perspective (by a couple) and also Dom and sub perspectives.

hope that helps.

Added: As an afterthought. If your partner runs for the hills, don't be devastated, it's probably not that they think you are bizzarre or have grown a second head. They may well have a different idea about what you are asking, they may not know what exacly you are asking for so try to let the dust settle and try again, explain if you are feeling hurt and try to explain making sure that they undersatnd what you are asking.

This is good practice for the honesty needed as things progress.