EXS 24 Logic Sampler Users Group

Hi everyone, new to this board, I have been recording my own samples 
from my classic keys module , and started with a mellotron sound, 
problem I encounter is finding a loop point of entry and end so I get 
no popping, am using exs24 II and logic 5.5.1 have searched on their 
page , in my books and now on here, some of the samples loop fine, 
but some don't and I know it has something to do with the crossfade 
point, however , I can't quite get it, any ideas???