Tips of ten to twenty percent are appropriate, and gifting American dollars is typically welcome. Many people lucky enough to visit Bhutan enjoy giving back to this magical place.
If you want to bring gifts, drop a book or two off at the Jigme Singye Wangchuk National Library on the main street, Norzin Lam, in Thimphu. The librarian will be grateful. High-end long black men's socks are good gifts for men, for they wear them with their national dress to cover their calves, and boxed teabags (herbal is great) are good presents to carry for the women you encounter. Most guides and all drivers, however, are men—at least, for now. People greatly appreciate a bit of the outside world being brought to them, since shops are not necessarily stocked with consumer goods from far away.