Maybe I am stating the obvious here, but in my experience, prior to controlling a submissives orgasm would come a profound knowledge of his/her likes and dislikes, capacity to orgasm. That alone can lead to devising ways to control orgasm. My "non-fictional" reading on the subject of human orgasm (I take Lord Douche's phrase for wont of a better one) would suggest that it cannot be controlled except by the orgasming person. Mentally, a person approaching orgasm blocks all sensation coming from outside and is totally focussed on his/her own person and needs. So another prerequisite to orgasm control would be the willingness of the submissive to let someone control his/her orgasm. But that is, from a fetish/role-playing point of view is defeating the real purpose, really. So, in real life, I guess, the farthest you can take this play is by having the submissive ask for permission to "cum" at a sufficiently early point on the climb towards fulfillment to be able to really stay in control.