I have one, I have one!

I have never owned a road bike before, but I now have a Raleigh Grand Prix with SunTour Power Shifters. The shifter cables are in bad need of replacing, but I can't seem to find any information on how to set the tension of the cables.

This might be personal preference, but should the paddles be all the way forward with the cable tight and ready to shift, or should they be standing straight up? When I bought the bike, the cables seemed a little loose and you could push the paddles forward all the way and there would be quite a bit of slack on both derailleurs... then again, the cables are rusty and probably stretched.

Help a newbie out