Sure, exploring Beijing, Shanghai, and Hong Kong will offer you a great insight into Chinese culture, history, and modern development. Here are some travel tips for you:

Best Time to Visit:
For a comfortable climate, the best times to visit these cities are Spring (April to June) and Autumn (September to November). Summers can be hot and humid, and winters can be quite cold.

Route and Accessibility:
Transit between these cities is convenient with numerous flights, high-speed trains, and buses. For instance, traveling from Beijing to Shanghai, a high-speed train would be a good option as it's economical and comfortable. Flights or ferries would be a good choice for the leg from Shanghai to Hong Kong.

Altitude and Acclimatization:
The altitude factor is not a significant issue in these cities, hence, no specific acclimatization required.

Accommodation and Booking:
Book your accommodations in advance since these cities tend to be quite busy. There is a range of options from luxury hotels, budget accommodations to guesthouses.

Clothing and Essentials:
Pack according to the seasons. Light, breathable clothes for summer; warm clothing for winter. Don't forget a good pair of walking shoes as these cities have some excellent neighborhoods to explore by foot.

Health and Safety:
Check that your travel insurance covers everything. Carry your prescribed medicines if you have any. Also, try to limit cash handling as much as possible. Diversify your money storage; take a mix of cash, cards, and traveller’s cheques.

Local Etiquette and Respect:
Chinese culture greatly values respect for others. Behave in an orderly fashion, and do not shout or cause unnecessary noise. Additionally, do be aware that tipping is not customary in China. Also, don't forget to respect their traditions and local regulations.