Hello! It's fantastic to hear you're planning a trip to Italy, encompassing sublime destinations like Rome, Venice, and Florence. Here are some travel tips to ensure a memorable trip.

Best Time to Visit:
The best time to visit Rome, Venice, and Florence is in the spring (April to June) or fall (September and October). The weather during these periods is usually mild and the crowd levels are lower, making sightseeing more pleasant. However, as these periods are considered the shoulder season, prices for accommodations can be somewhat higher.

Route and Accessibility:
All three cities are well-connected by high-speed trains. You can start your trip from Rome, then travel north to Florence, and finally reach Venice. All cities boast good public transportation networks, including metros, buses and, in Venice, public water buses ('vaporetto'). Make sure to buy a public transport pass for unlimited travel within a certain time period.

Accommodation and Booking:
Each of these cities has a wide array of accommodations ranging from luxury hotels to budget hostels. I recommend booking your accommodations in advance especially during the peak tourist seasons. Sites like Booking.com or Airbnb are useful to find and reserve your stay.

Clothing and Essentials:
Pack comfortable footwear as there's much to explore on foot, particularly in Rome and Florence. Light, breathable clothing is recommended for the summer months, while layers are a good idea for the cooler spring and fall months. Don't forget accessories like a good-quality sunhat, sunglasses, and sunscreen.

Health and Safety:
Italy is generally safe for tourists, yet, as with any travel, maintaining a degree of caution is advisable. Keep your valuables secure, stay in well-lit areas at night, and maintain awareness of your surroundings. Basic travel insurance that covers health, theft, and cancellation is always a good idea.

Local Etiquette and Respect:
Italians appreciate polite manners. Say 'please' ('per favore') and 'thank you' ('grazie') frequently. Cover your knees and shoulders when visiting churches. Tipping isn't mandatory in Italy, but it’s appreciated for good service in restaurants and for taxi drivers.