Sure, I'd be happy to help you plan your trip to Casablanca, Marrakech, and Rabat. Here are some tips for your upcoming journey.

Best Time to Visit:
The best time to visit Casablanca, Marrakech, and Rabat in Morocco is during spring (April to June) and autumn (September to November) when the weather is pleasantly warm.

Route and Accessibility:
Most international flights land in Casablanca, making it an accessible start to your journey. From there, domestic flights, trains, and buses connect Casablanca to Marrakech and Rabat. If you prefer, renting a car is also a good option.

Accommodation and Booking:
Accommodation in all cities ranges from luxury hotels to budget guesthouses. It's always best to book in advance, particularly during peak tourist seasons. Sites like Booking.com, Airbnb, and local travel agencies provide a wide range of options.

Clothing and Essentials:
Morocco has a strong Islamic culture, and it's advisable to respect this in your choice of clothing. Women should pack a scarf for covering the head in mosques. Also, pack sunscreen, sunglasses, and a hat for protection from the sun.

Health and Safety:
It's generally safe to travel in these cities, but as with any destination, it's important to stay cautious. Avoid drinking tap water and stick to bottled water. Also, consider travel insurance that covers emergency evacuation, as remote areas might not have accessible medical facilities.

Local Etiquette and Respect:
Respect the local religion and traditions. During Ramadan, eating, drinking, and smoking in public during daylight hours should be avoided. Moroccan's speak a mix of Arabic, Berber, and French, so hello can be said as 'Salam' or 'Bonjour'.