Sure, I'd be happy to help! Here are some travel tips for your visit to Beijing and Tianjin:

Best Time to Visit:
The best periods to visit Beijing and Tianjin are during spring (April - June) and autumn (September - October). During these time periods, the weather is relatively comfortable and you can avoid the extreme temperatures of the Beijing summer and winter.

Route and Accessibility:
Both destinations are very well connected by trains and flights from all over the world. Beijing and Tianjin are just 30 minutes away by high-speed train. From Beijing Capital International Airport, you can catch a taxi, airport shuttle, or take a train to reach the city center.

Altitude and Acclimitization:
The altitude of both cities is quite low (Beijing: 43 m; Tianjin: 2 m), so you won't need to worry about acclimatizing to high altitudes.

Accommodation and Booking:
Both Beijing and Tianjin have a wide array of accommodation options ranging from budget hostels to high-end international hotels. It's advisable to book in advance particularly if you are visiting during peak tourist season.

Clothing and Essentials:
Depending on the time you choose to travel, you should have appropriate clothing. During spring and autumn, light jacket and jeans should suffice. But Beijing's winter is quite harsh, so lots of thick, warm clothing is a must if you plan to visit during December - February.

Health and Safety:
Healthcare facilities are of a high standard in these cities. Remember to purchase health insurance that covers any medical expenses, evacuation, and any activities you plan to do. Be aware of the traffic in both cities. Pedestrians should be careful while crossing roads.

Local Etiquette and Respect:
Chinese people appreciate politeness. A simple 'Ni hao' (hello in Mandarin) can bring a smile to people's faces. Also, respect local customs and avoid talking about sensitive topics.

Don't forget to sample the local cuisine! Peking duck in Beijing and Goubuli buns in Tianjin are a must-try! Enjoy your trip!