I very rarely punish. But I have to agree with Timberwolf that denial is probably the best form of net punishment I can imagine. If the attachment and devotion are there, the lack of contact is a good way to punish.

I also think that for most submissives, the simple knowledge that they have failed to meet the expectations of their Dom is usually enough punishment in itself. My R/L Sub/wife will tell you that for me to tell her that I am disappointed in her behavior or her actions, or that I felt that she let me down in the way she acted, is more devastating to her than any physical punishment that I could inflict.