In addition to the official NWN forums that have alot of threads about character builds, there is also a shifter guide over at
GameFaqs.com.
From my limited knowledge of shape shifters, I can only suggest that you leave your combat stats (STR, DEX, CON) pretty low if you plan on being shape shifted most of the time. Most of those stats are overridden when you take other forms, so concentrate instead on INT, WIS, & CHA unless you want to get certain combat feats that have prerequisites (Power Attack, Cleave).