The local currency, dalasi (D), fluctuates strongly. It's best to have hard currency (British pounds, euros or US dollars) on hand and exchange it as needed. ATMs exist on the coast, but are not practical.
Restaurants Tipping isn't expected at smaller local restaurants; at more touristic places, a 10% tip is fairly common.
Guides At many reserves and parks, guides will be available – sometimes even included in the admission price. Regardless, it's always polite to tip the guide. While it's hard to give guidelines, D50 or more per hour is a benchmark.
Bumsters Don't tip people who hassle you or harass you for money.