Sure, here are some tips for your journey to Isfahan, Yazd, and Shiraz, three of Iran's most beautiful and historic cities:

Best Time to Visit:
The most ideal time to visit these cities is during Spring (March, April, and May) and Autumn (September, October, and November) when temperatures are moderate and pleasant.

Route and Accessibility:
Isfahan, Yazd, and Shiraz are well-connected by road and air. You can travel between cities by domestic flights, buses, or taxis.

Altitude and Acclimatization:
The elevations in these cities are not very high (1,500-1,800 meters), so you are unlikely to experience altitude sickness.

Accommodation and Booking:
It's advisable to book your accommodations beforehand to avoid last-minute inconveniences. There are various options, ranging from budget hostels to luxury hotels.

Clothing and Essentials:
Iran has strict dress codes, especially for women who are required to wear a headscarf and cover their bodies. For men, shorts and sleeveless shirts are not permitted. Be sure to pack light, loose clothing for the unavoidable heat.

Health and Safety:
Before traveling, ensure your vaccines are up-to-date. Always carry a first aid kit and any personal medications. Avoid drinking tap water and opt for bottled water instead.

Local Etiquette and Respect:
Respect local customs and traditions. Always greet locals with a simple "salam". It's common to remove shoes when entering homes and mosques.
Haggling over prices at markets is common, but done in a friendly, good-natured way.