I don't know the PROPER way to do it, but we always hand deliver
tips at the end of the cruise. (in addition to the auto-tips).
We generally give at least $5, but have gone over $50 on occasion.
One couple we traveled with recently tipped the Room Dude $100,
but that is way over my budget.
The Room Dude is not hard to find, just look outside your cabin door
the last evening of the cruise.