The short answer
Ask the riad to meet you. Most riads will send someone to the nearest gate, square or taxi drop-off and walk you in, which is the surest way on a first night. On your own, use an offline map with the riad pinned, and learn its nearest gate (bab) and one big landmark close by.
In more detail
The derbs twist, double back and rarely follow a grid, and even people who know the city get lost. Download an offline map before you arrive and drop a pin on the riad while you still have wifi. Note the nearest gate and a landmark such as Jemaa el-Fnaa or the Koutoubia minaret, so a taxi can get you close.
Be ready for offers of help. If you look lost near a junction, someone, sometimes a child, may offer to lead you and then expect a tip, or steer you towards a shop. A polite, firm 'la, shukran' (no, thank you) and walking on with confidence is the usual answer. If you want a guide, ask your riad to arrange a licensed one.
With a pre-booked transfer the problem mostly disappears. A driver who knows the medina parks at the closest point and walks you, or hands you and your bags to a porter, right to the riad door.
Good to know
- Screenshot the riad's own walking directions from the gate.
- Walk the route from the gate once in daylight on your first day.
- If you are lost, ask in a shop or café rather than someone who approaches you.