If we talk about the best places to visit in Himachal, it is almost impossible to say because each and every places of the Himachal is paradise.
I have categorized the Himachal in 4 division.
1: Shimla Region: The Capital City of Himachal, It includes the tourism of Kufri, Narkanda and Shimla itself, this is the complete package for families, couples and beginner travelers. It is not very expensive but in peak time tariffs of hotels exceed 4 times as per regular rates.
2: Manali: This is the most commercial place of Himachal, it includes the tourism of Kullu, Rohtash, Solang, Hampta Pass and Manali itself. It is the sufficient package for travel enthusiasts. This is also a dream destination for the bike riders to cover Leh-Ladakh via Rohtang Pass and Sarchu.
3: Kasol: Best place for the treking purpose, especially for the friends group. It includes Manikaran, Kheerganga, Tosh and Parvati Valley.
4: Spiti and Lahaul: In my perception, this place is the perfect paradise for everyone. One of the most adventurous place of India even more than Mahal-Leh. In my categorization this division includes 7 more beautiful heavens like Chitkul, Kinnaur Kailash, Kaza, Nako, Tabo, Pin Valley and Sangla. According to me this is the best part of Himachal Pradesh in which you can feel everything which any traveller wants.
