Hi there! Your trip to Vilnius, Riga, and Tallinn sounds like an exciting adventure. Here are some travel tips to assist you.

Best Time to Visit:
The best time to visit Vilnius, Riga, and Tallinn is from May to September when the weather is warm and the cities are lush and vibrant. These cities also host a range of festivals during this period.

Route and Accessibility:
All three cities have international airports making them easily accessible. Buses and trains are also good options when moving between these cities, providing picturesque views of the country sides.

Accommodation and Booking:
There are a variety of accommodation options in all these cities ranging from luxury hotels to budget-friendly hostels. Booking online in advance is recommended, especially during peak season.

Clothing and Essentials:
Pack light summer clothes for the warmer months but do carry a jacket for cooler evenings. An umbrella and waterproof shoes are a good idea due to occasional rainfall. Don't forget your camera and a good guidebook or maps for the cities.

Health and Safety:
The cities are generally safe but basic precautions should be taken. Make sure your health insurance is valid in these countries and you have access to necessary medical facilities.

Local Etiquette and Respect:
People in these cities appreciate good manners and respectful behavior. Try to learn a few phrases in Lithuanian, Latvian, and Estonian as it could endear you to the locals.