Sure, I'd be happy to help with your travel to Freiburg, Triberg, and Tübingen. Here are some travel tips for your visit:

Best Time to Visit:
The best time to visit Freiburg, Triberg, and Tübingen is between May to September when the average temperatures range from 20°C to 30°C. These cities are picturesque throughout the year, however, spring and summer are particularly beautiful with blooming flowers and greener landscapes.

Route and Accessibility:
The easiest way to reach Freiburg is via flight to EuroAirport Basel-Mulhouse-Freiburg followed by a bus or train trip to Freiburg. From Freiburg, you can take a train to Triberg, and from Triberg, a train to Tübingen. Public transportation in these cities is reliable and efficient.

Accommodation and Booking:
You will find a range of accommodations in all three cities, from luxury hotels to budget-friendly hostels and vacation rentals. Booking.com, Expedia, and Airbnb are reliable platforms for booking accommodations. Try booking in advance for better deals.

Clothing and Essentials:
Pack clothing according to the season. Summers would require lightweight clothing, sun protection gears like hats, sunglasses, and sunscreen. During winter, warm clothing including thermals, jackets and boots are essential. Don't forget your comfortable walking shoes, a universal power adaptor, and a good camera!

Health and Safety:
Standard health and safety advice apply, including having travel insurance, keeping emergency contact numbers handy, and maintaining regular hydration. Remember to bring any personal medication and a basic first aid kit.

Local Etiquette and Respect:
German people appreciate politeness and punctuality. It's important to greet people and thank them. Also, remember to respect local traditions and the natural environment, especially when hiking in the Black Forest.