Room Service: I always ask specifically how much of the tip/service charge goes to the server directly, then adjust to net 18-20%. I've sensed disappointment on occasion when the delivery person realizes they aren't going to get a tip on top of a tip. Other times, the delivery person has explained the service charge prior to my even asking.

Bellman: I sometimes use the bellman to deliver boxes that have been delivered to the hotel or store bags. When it's boxes, I tip $5 for up to two boxes, $10 for more. If there are more than six boxes, the tip goes up.

Maids: I do not tip.

Parking Valet: $3 in and $3 out.

The above is based upon what I can get reimbursed for, per our company's policy. Note that waitstaff, which would include room service delivery, is usually paid a much lower minimum wage ($2.13/hr in most states) and taxed based on tips as a minimum percentage of food sold. Bellman and Valets are also likely being paid the tip wage. That is not the case with housekeepers, who are not eligible to be paid that low wage. That's a big, important difference.