hi,
   load line means load device characteristics,lets take common source amplifiers,in that resister  character sics are load line.Where as in inverter(cmos inverter),if u assume nmos  as amplifing device,then pmos is load and pmos characteristics are load curve,where as for opposite assumption nmos characteristics  are load curve.I hope u understand.

Regards,
Rajasekhar.

hi,
   that will come with experience,some information u can  get in analog ic design by allen holberg,even i too learn from some body elae when i was a in undergrad.So keep asking such a basics rather trying to read from books
Regards,
Rajasekhar.