skiing can be done in three places as per my knowledge....
1- Naltar : these dayz its best as snowfall has reduced in Mallam Jabba and also the facilites are hone with the PTDC motel destruction....
2- Mallam Jabba: easy to reach but above mentioned reasons are there...
3- Rattu: u need some army pawa and a big one... they got all gear there u ll get proper snow...
i dont know any techincal issues abt skiing so this is all i can help with......
also FEB is ideal as max snow falls