Sure, I'd be happy to help. Here are some travel tips for a visit to Hanoi, Sapa, Cúc Phương in Vietnam:

Best Time to Visit:
The best time to visit Hanoi is during the dry season from October to April when temperatures are moderate. In Sapa, the best time for trekking is after the rice harvest in October & November or before the planting season in March & April. Cúc Phương National Park is best in the dry months from December to April.

Route and Accessibility:
Hanoi’s international airport connects it to many parts of the world. From Hanoi, direct sleeper buses and trains are offered to Sapa. To get to Cúc Phương, it's just a few hours drive from Hanoi.

Altitude and Acclimatization:
Hanoi and Cúc Phương are at sea level, so there won’t be any altitude issue. Sapa is a hillstation and sits at a height of about 1500 - 1650 meters above sea level, the gradual ascent to Sapa does not require dedicated acclimatization.

Accommodation and Booking:
Hanoi has a diverse range of accommodations. Sapa offers a variety of homestays in local villages, which can be a great cultural experience. Cúc Phương offers park accommodation like guesthouses and tents. Book in advance especially during peak seasons.

Clothing and Essentials:
Clothing should be dependent on the season you are travelling. Also, pack a good pair of walking shoes for trekking in Sapa & Cúc Phương. Carry a raincoat, sunscreen and insect repellent.

Health and Safety:
Practise good personal hygiene and eat from reputable establishments to avoid traveler's diarrhea. Don’t forget to carry travel insurance and your own personal medical kit.

Local Etiquette and Respect:
Respect Vietnam’s customs and traditions. Avoid wearing revealing clothing in rural areas and when visiting temples or pagodas. Be conscious about environmental preservation, especially when visiting the national park.