Hello there! Your trip to Hammamet, Sousse, and Mahdia sounds exciting. Here are some useful travel tips for you.

Best Time to Visit:
The best time to visit Hammamet, Sousse, and Mahdia in Tunisia would be from April to June and from September to November when the weather is pleasant and not too hot. July and August are the peak tourist season, so if you prefer less crowd, avoid these months.

Route and Accessibility:
You can reach Tunisia by air, land, or sea. Hammamet is 73 km away from the Tunis-Carthage International Airport, and you can reach it by taxi or rental car. Sousse and Mahdia can also be reached via the road network from the airport.

Accommodation and Booking:
There's a broad range of accommodations available in these cities from luxury resorts to budget hotels and apartments. It's generally recommended to book your accommodation in advance, especially during peak tourist season.

Clothing and Essentials:
Pack light clothes for daytime and warmer clothes for cooler evenings. Don't forget to carry swimwear, a hat, sunglasses, a high SPF sunscreen, a travel adapter, and a good insect repellent.

Health and Safety:
Ensure that you're up-to-date with routine vaccines before the trip. Be cautious about food and water hygiene, and ensure personal safety and security, especially while visiting crowded places. It is advisable to have travel insurance in case of emergencies.

Local Etiquette and Respect:
Tunisians are warm and welcoming. Respect their customs and traditions. Dress modestly, especially in religious places. Giving a warm smile and polite 'thank you' in Arabic that is 'Shukran' would be appreciated.