Sure, I'd be happy to assist you with your travel planning for Manali, Shimla, Dharamshala, and Agra.

Best Time to Visit:
The best time to visit these destinations varies. For hill stations like Manali, Shimla, Dharamshala, the ideal time is between March to June. For Agra, it's recommended to visit between November to March, to avoid the extreme summer heat.

Route and Accessibility:
You can first fly to Delhi, and from there, you can either take a train or a bus to Shimla, Manali, and Dharamshala. From Dharamshala, you can get a bus or taxi to Shimla and Manali. Agra is easily accessible from Delhi via road and rail.

Accommodation and Booking:
For accommodation, book your hotels in advance via online booking platforms or travel agencies. There are various types of accommodations available, from luxurious hotels and resorts to budget guesthouses and homestays.

Clothing and Essentials:
Since climates can be diverse across these locations, pack a mix of both light and warm clothing. Carry a sturdy pair of shoes for trekking if you plan to do so in Manali or Dharamshala. Don't forget to pack your essentials like sunscreen, sunglasses, and medications.

Health and Safety:
Carry essential medicines, especially for altitude sickness if you're susceptible to it. Stay hydrated and be careful while venturing out into the wilderness or on treks. Make sure you have travel insurance.

Local Etiquette and Respect:
Indians appreciate respect towards their traditions and customs. It's important to dress modestly at religious sites. Always remove your shoes before entering a temple. Take the consent of people before taking their photographs.