Workers in restaurants and hotels earn little. You can help matters a bit by ensuring that those who work for you get a good tip. The directive is (at least if satisfactory service is delivered) 1 euro per passenger per day gratuity for the staff of the hotels. For the drivers of the vehicles Shoestring hires and local cook who travels with you, a similar amount is fine. It is a good idea to have a pot for these tips, managed by the travellers in consultation with the tour leader. In eateries etc. you can leave a tip of 5 to 10% of the amount payable. Also, drivers of taxis and shuttles, guides and people on the street providing a service, expect a fee. Never pay in advance!
The tour leader at the end also expects a tip, if she/he has done well. Shoestring pay the tour guide a wage that is flush with that of most adventure travel companies, but that's still low. Our guideline for tipping is € 1 per passenger per day.