asterisk users - Jul 2005 - personal voicemail , and call transfer --- howto

Could someone please help me to understand how to
a) customize voicemail ..... so that I can say "Hi this is Allan, not in 
right now ..... "   . I have read that one can press 0 to get to the 
voicemail menu..but I cant figure at what point to press 0 to get to 
this menu.
b) also .... what key sequence to transfer calls on asterisk .... where 
is this documented ?

TIA ... Allan