We visited Czech Republic in December, which means the region was ice-cold. We mainly went during that time to experience the famed Christmas Markets in this part of the World. There are disadvantages to visiting Czech Republic during Winter:
(1) Some sights will be closed for the Winter. E.g. We could not enter the Cesky Krumlov Castle.
(2) Those who love greenery will miss it 🙂 While travelling through Czech Republic and Austria, it struck me that these areas must be just spectacular during Summer. (As Terminator says, “I will be back!” :-))
Prague Castle requires at the very least 4-5 hours to explore. It is best to go as early as you can, because once the crowds get it, some of the internal sights get really crowded. E.g. Golden Lane and St. Vitus Cathedral. There are several Souvenir stores, paid restrooms and cafes within the Castle Complex.
We took the Prague Metro to Malostranská station and walked up to the Castle. You can also take the Trams right up to the Castle, if walking uphill is not your thing. We wanted to stroll the streets in that area and hence preferred to walk up to the Castle.