Hello! That sounds like an exciting trip. Here are some travel tips for your visit to Tehran, Shiraz, Tabriz, and Yazd.

Best Time to Visit:
The best time to visit Iranian cities like Tehran, Shiraz, Tabriz, and Yazd is during the spring (late March to early June) and autumn (late September to early November) when the weather is pleasant and the temperatures aren't extreme.

Route and Accessibility:
All these cities have international airports, so you can choose to fly directly into Tehran, which has the largest international airport, and from there take domestic flights to the other cities. Also, Iran has a well-connected rail and road network which you can use for inter-city travel.

Accommodation and Booking:
All these cities have a wide range of accommodation options ranging from budget guesthouses to luxury hotels. Booking can be done online through hotel booking websites. It's advised to book in advance, especially during peak seasons.

Clothing and Essentials:
Remember that Iran is an Islamic country, hence modest clothing is expected. Women are required to wear a headscarf and clothes that cover the arms and legs. Also, don't forget to pack sunblock, sunglasses, and a hat for the sun-drenched days.

Health and Safety:
Ensure you are up-to-date with routine vaccinations before your trip. Hand sanitizing and wearing masks in crowded places can protect you from local diseases. Drink only bottled water and eat freshly cooked food.

Local Etiquette and Respect:
Iranians are very hospitable people. It's respectful to follow local customs such as greeting people with 'Salam', saying 'Merci' for thanks, and removing shoes when entering someone's house. Avoid discussing political issues.