Dakar is one city where it's definitely a good option to make a reservation before you arrive. Depending on where you're coming from, there's a good chance you'll be arriving after dark, or even late into the night, which can be a little intimidating. It's worth the peace of mind to have reservations ahead of time, and already have arranged an airport pickup. You'll pay more, but sometimes it's worth the extra bucks. Do read reviews of your hotel before you book. Options are variable in quality.