Absolutely, I'd be happy to assist. Visiting Vienna, Salzburg and Eisenstadt in Austria will offer you a blend of rich history, breathtaking landscapes, and vibrant art and music culture.

Best Time to Visit:
The best time to visit Austria is either from April to June or September to October. The mild weather in spring and fall is great for exploring the cities and the countryside. However, if you are a winter sport enthusiast, December to March offers great skiing conditions.

Route and Accessibility:
Vienna's Airport is the most accessible for international tourists. You can then take the train or bus to reach Salzburg and Eisenstadt, as public transportation in Austria is excellent.

Altitude and Acclimatization:
The altitude is not a significant consideration regarding these Austrian cities, as they're not located at high altitudes.

Accommodation and Booking:
Booking your accommodations well in advance is highly recommended to secure the best rates. There are numerous options ranging from luxury to budget hotels, bed & breakfasts, and apartments.

Clothing and Essentials:
Depending on the season of your visit, pack accordingly. For spring and fall, pack layers and a light jacket. If you're visiting in winter, ensure to carry warm clothing, winter boots, hats and scarves. Don't forget your comfortable shoes for walking around the cities and exploring.

Health and Safety:
Austria is considered a safe country to travel to. However, like with any travel, it's always wise to have travel insurance. Also, keep emergency contact numbers handy.

Local Etiquette and Respect:
Austrians greatly appreciate good manners. A firm handshake is the general greeting and it’s polite to say 'Guten Tag' (Good Day) when entering shops and restaurants. In theatres and opera houses, refrain from talking during the performance. Lastly, remember to respect the environment, especially when visiting rural and mountainous areas.