Nearly everyone who goes to Amizmiz gets there via Marrakech. Within Marrakech, you'll need to take a "petit taxi" to the "Bab Er-Rob" taxi station that is just outside of town. Once you arrive at the taxi station, start asking for "Amizmiz" (which is pronounced AMZ-meez), and someone will eventually direct you to a "grand taxi" (an old Mercedes Benz) that is waiting to get filled up, at which point you'll depart. The normal fare is 12.5 Dirham. You can also find a "mini-bus" that takes a lot longer (because of more frequent stops) which costs only 10 Dirham. For those who are not as eager to sit squished for an hour's ride in the heat, feel free to pay for two places (hence 25 Dirham) and ask for the front passenger area to yourself (normally two people sit in the front passenger seat!).
Once you arrive at Amizmiz, you'll be able to get everywhere by foot.