Do I need to make advance reservations to go up? I'm will be there in September only for 2 days and want to do this for sure.
Reservations are much cheaper and its online. The slots get filled up pretty fast.
You,l always get tickets right there at the counter, but for 4 times the price.
Make sure to go at perfect whether conditions to enjoy the sight.
You can purchase them on the spot but you can purchase the tickets at a discount online. Also the sunsets time slots fill up quickly so booking in advance is your best chance at going up at that time. That way you can see the city in the light and with the lights and water show below at night.
you will find your answer here http://www.burjkhalifa.ae/en/ObservationDeck/TicketInformation.aspx