As your trip in Bhutan will be organised by a local agent, you don't have to tip in hotels or restaurants.

On treks it is customary to tip the cook, his aide and sometimes the horsemen.  Ask your guide what and how much is right.

You should tip your driver and guide who are with you for the whole trip.Better be careful not to insult with small tips. Sometimes it is by tradition that the tip receipient will shy away from receiving the tip given but as a Bhutanese tradition offer it the second time and it will be accepted.

When buying, bargaining is unusual. Sometimes the seller will give a discount when more than one item is bought. One should be careful in buying any item of antique value which can be seized by customs on departure and should seek guidance from your guide who can advise.

The Bhutanese economy has sufferred rising inflation for several years now and living expenses in the capitol of Thimphu have dramatically risen--inflation was eight percent in the first quarter of 2013.  So the going tip for guide and driver has risen to $20 per day for the guide and $10 per day for the driver.