Room Service - Usually tip 10% unless the tray charge was big. Certain less fortunate countries where I know the staff struggle to get by I've tipped up to 30-40%. I was once kept waiting in an Australian hotel and my order came up 2 hours after it was ordered and I disputed the tray charge.

Bellman - I NEVER use this service, one is an issue of trust and two I'd rather get changed and shower as soon as I enter the room.

Maids - I don't tip housekeeping.

Parking Valet: Rarely use this service but if I do then $5 each way.