Only ever max Cha if you need it.  IE have to order things around, even then unless you are in a tribunal it is generally not necessary to max!  If you are a fighter STR DEX CON HP - caster WIS INT MANA ART (sometimes art comes first, depending on your build)  Art is really handy because it makes spells hit with full damage more often.  I generally stay away from CON on casters, but others swear by it.  The way I see it, without heavy armor or a bunch of defensive skills it is kinda pointless...  Naturally you would not want REALLY low con, but mid range is fine in my book. 
