The nearest airport is Stuttgart (STR). From here you can take a train to Stuttgart Hbf (27 minutes) and then take a second train to Mannheim Hbf (37 minutes) before transferring to a third to Mannheim ARENA/Maimarkt (4 minutes). The festival is then a short walk from here (13 minutes).
Amsterdam - Stuttgart (1 hour 10 minutes)
Vienna - Stuttgart (1 hour 10 minutes)
Berlin - Stuttgart (1 hour 15 minutes)
Paris - Stuttgart (1 hour 25 minutes)
London - Stuttgart (1 hour 35 minutes)
Madrid - Stuttgart (2 hours 25 minutes)
The closest train station is Mannheim ARENA/Maimarkt, usually reached via Mannheim Hbf.
Frankfurt - Mannheim ARENA/Maimarkt (41 minutes)
Nuremberg - Mannheim ARENA/Maimarkt (2 hours 46 minutes)
Munich - Mannheim ARENA/Maimarkt (3 hours 5 minutes)
Zurich - Mannheim ARENA/Maimarkt (3 hours 7 minutes)
Paris - Mannheim ARENA/Maimarkt (3 hours 15 minutes)
Berlin - Mannheim ARENA/Maimarkt (5 hours)
The festival can easily be reached via car and there is parking directly opposite the site. There is a parking fee of €5 for each day of the festival to be collected by the car park operators.
You are not allowed to barbecue on the festival grounds however it is permitted in the campsite.
Open fires are not allowed and you must dispose of carbon (and other waste) at the designated locations.
Yes, however professional cameras (SLRs etc.) require permission from the festival organisers.