Bring a supply of euros (preferred over US dollars). Some ATMs accept international cards. Banks and hotels in the capital can organise changing money.
You'll often be asked for a cadeau (gift), whether you've been helped or not. It's up to you to decide whether it's appropriate in return for services rendered.
Hotels At top-end hotels, one gratuity for cleaning staff, completely at your discretion.
Restaurants None expected at basic places; upscale, with decent service, 10% to 15%.
Taxis Loose change appreciated.
Guide & Driver Always expected, around 10% or more if especially good and for multiday trips.