Room service: Recently I've seen (and being pointed out by person delivering food) that it is already included. In which case I do not add tip on top of it. Otherwise I do my standard multiplying the digits above single digit (i.e 1x.xx would be +$2, 2x.xx would be +$4 ...).

Bellman: $1 per bag. I only use this service when traveling with my family, usually toddler has several and it ends up in $5-10 range.

Valet: $2-5 depending.