Know what the event is
It goes without saying that if you want to photograph a festival, you should know what the festival is all about! You should know how it originated, what it commemorates, and what the significance is, in relation to the current times. Armed with this knowledge, you could decide your “workflow” – the series of pictures you should take to record the event without missing out on any important picture taking opportunity. In other words, do your homework and plan out your strategy rather than going to the festival and then taking photos haphazardly. If you are new to the location or if you have not covered such a festival earlier, it would be wise to ask the locals about the path of the procession, the type of ceremonial floats, the time for the event to start, and whatever other information that you think will help you in your picture-taking project. If you can check out the details with the organizing committee, so much the better, as the information could be more specific, and more reliable. All this takes time, so make sure you don’t think of ‘what-am-I-supposed-to- do’ at the last minute. Remember though, a festival may not necessarily have a parade and floats.
~Rohinton Mehta from his article How To Photograph Festivals