Yemen is country that everywhere just simply must be visited. It is a tourist’s country, where although the accommodation might not be the best, but the country itself holds so many treasures that appeal to any open-minded visitor.
Tourists are expected to give pens (referred to as qalam or galam) for the local school. Sweets are also acceptable.
Source: http://www.travelingeast.com/middle-east/yemen/ten-interesting-facts-about-yemen/, http://wikitravel.org/en/Yemen