What signs should I look for that would give me a clue on when I should change my brake pads. I know when they grind you've gone to far, I made that mistake once. But back to the point, how can I tell when it is time to change my brakes, both front and rear?  

either inspect them every few months... or listen to the squeel that goes away when you step on the brake pedal....

the squeel is caused by the little finger of sheet metal that can contact the rotor face when the pads wear thin....

and please.. if you are going to use silicone to lube the slides or pins... use silglide.. not silicone dielectric compound...   i have had several brake jobs come through that somebody put the dielectric grease on them... the slides locked up so tight that i could not even use a 30 ton press to move it... and thats tight...  

Thanks for the info. Especially about the grease. I have some tell me to use it and some who tell me not to.