I think the rule of thumb is $1 per bag for each person who touches your bags, so if you get assistance at the airport, you'd tip them. If you use ME, I don't think it's expected to tip your driver and since your bags may just arrive in your room when you're not there, you wouldn't tip then either. When we've stayed Deluxe and Bell Services has brought our bags from our car, we've tipped $1/bag.