Berlin has three airports: Tegel (TXL), Tempelhof (THF), and Schönefeld (SXL). Tegel will be the airport where you will arrive (mostly). The easiest but also most expensive way to get to ph-neutral from the airport is by cab.
Taxis (how cabs are called here) are available at all airports. Price from Tegel Airport to ph-neutral will be around 30-35 Euro. For details about cabs in berlin see cab page.
For information on how to get from the airport to c-base (where ph-neutral takes place) with public transportations, is check out the public transport page, the airport information from BVG at: http://www.bvg.de/plan/e_flughafen.html. You may also want to use the online journey planner to find a connection.
There is some more information about Berlins airports at the Berlin tourist info airport page.