Winter is over and the sunshine makes days more optimistic. Use alarm clock app in your mobile to get up early morning :-). Everything will be more plastic in the morning light and the historical centre of Prague is not overcrowded. Evenings are good as well, but not during the high season. Also avoid weekends, when the crowds are enormous. The second important app is Pocket Fennec - your audio city guide. You can go, listen the great stories and admire the historical beauty of the city.