Radio 1's Big Weekend is about to get going in Sefton Park, Liverpool. Each year the station rounds up some of the hottest artists in the world and gets them together for three days of music in a UK city. But with about 100 acts across four stages, there's a lot to take in. So BBC Newsbeat spoke to DJs Greg James, Sian Eleri and Jack Saunders to get their top tips on what to watch out for.