I visited Manali as part of my family trip in May, 2013 just after finishing my college. If you go to manali you will be definitely lost in nature it’s very good place.
It is accessible from delhi or chandigarh via bus or you can book a cab.
In sightseeing these are so many place but I would tell the famous and must visit places as the first is Rohtang pass, this place will take whole day but it is worth more than that. In May also it was fully covered with snow and it reminds you the heaven on earth. In manali also you can visit local market, vashisht for hot water springs, hidimba mata temple, club house, soling valley and all you see is good.
Please do try Sidku as it is very tasty and I liked it very much.
Do stay in any good hotel like Holiday-In, Sterling resort or any other whichever you find easily.People are very gullible here and very nice to tourists.
Just do visit manali and you will see the real beauty of a hill station and will forget others.
I will also write a blogs with picture on himachal tourism and will post the link in comment soon.