Hello! That sounds like an exciting trip to Japan you have there. Here are some travel tips:

Best Time to Visit:
The best time to visit Sapporo, Asahikawa, and Hakodate in Hokkaido depends on what you want to see. For the snow festival and skiing, late January to February is the best time, but if you want to avoid the cold and enjoy the summers, July to August is ideal. The autumn foliage from late September to early November also offers a breathtaking view.

Route and Accessibility:
The three cities are well connected via trains and buses. From Tokyo, you can fly to Sapporo's New Chitose Airport or take the JR Shinkansen (bullet train) to Hakodate and then a connecting train to Sapporo or Asahikawa. Exact routes will depend on your initial location and further planned destinations.

Accommodation and Booking:
These cities offer a wide range of accommodation options from budget hostels to luxury hotels. It's recommended to book your accommodation in advance, particularly during the high seasons like the Sapporo Snow Festival or the cherry blossom season.

Clothing and Essentials:
Appropriate clothing depends on the time of your visit. For winter, heavy snow wear is a must, while summers are mild and light clothing is appropriate. Don't forget a good pair of comfortable shoes for exploring, and an umbrella or rain jacket as Hokkaido can be rainy.

Health and Safety:
Japan is generally safe and clean, but it's always wise to have travel insurance that will cover medical expenses. If you have specific dietary needs, be aware that English menus and English-speaking staff are not always available.

Local Etiquette and Respect:
Japanese culture places a great deal of importance on respect and politeness. It is good to familiarize yourself with some basic Japanese phrases. Be aware of local customs like removing your shoes before entering homes or certain restaurants, and avoiding loud or disrespectful behavior.