Absolutely! Here are some travel tips to assist you with your journey to Lisbon, Madrid, and Barcelona.

Best Time to Visit:
The best time to visit these cities is during the spring (March to May) or fall (September and October). During these times, the weather remains moderate and there aren't too many tourists.

Route and Accessibility:
You can start with Lisbon, then head to Madrid, and finally round up your trip in Barcelona. There is a good network of trains and flights connecting these cities.

Altitude and Acclimatization:
Lisbon, Madrid, and Barcelona are at lower altitudes so there isn't much to worry in terms of acclimatization. However, do make sure to pace yourself according to your fitness level as exploring these cities can require a lot of walking.

Accommodation and Booking:
Consider booking your accommodations in advance through reputable sites. All three cities have a wide range of options from hostels to luxury hotels.

Clothing and Essentials:
Regardless of the season, pack comfortable walking shoes. If you're visiting in winter do pack warm clothing, on the other hand, if it's summers a hat and sunscreen can be useful. A travel adaptor is also important as the plug type in these countries is different from other countries

Health and Safety:
Keep a close eye on your belongings as theft can be common in crowded areas. Purchase travel insurance that covers health just in case. Try to avoid late-night strolls in less crowded areas.

Local Etiquette and Respect:
These cities have a laid back culture. However, do remember to respect local rituals, the language and display proper etiquette such as not speaking loudly or causing disturbances. In Spain, afternoon siesta is observed religiously, do check the opening times of the places you wish to visit.