my Wife has three rules that apply at all times:
1. Say it out loud to Her. If i have a fantasy or a craving, whatever perverted, disgusting thing i want Her to do to me, i have to tell Her. Immediately.
2. Ask Her for it. Telling Her what i want isn't enough - next i have to ask for whatever i want. In person, naked, on my kneels, without any sign of an erection (She has a strict rule against erections without Her prior permission).
3. Let Her decide. my Wife frequently reminds me that part of my submission is accepting Her judgment about what i want, and what i need. She decides whether i get what i asked for, or something else, or nothing at all. She separates my wants from my needs, and treats each according to Her whim.
So yesterday afternoon i crawled naked into Her studio and begged Her to let me hurt myself with metal alligator clips on my nipples. She glanced up from Her work, said yes, and removed Her socks before She continued Her crafting. i spent the next 15 minutes sucking and licking Her Feet while She ignored me and my groans of pain.
When She had enjoyed my mouth enough She told me to stop. Of course i had a stiffy. The punishment spanking (with a wooden paddle) was hard enough to leave me sore for the rest of the day.