2000 Chevy S-10 Hard starting with slow cranking.?

[kerry]

I have a 2000 chevy s-10 witha 2.2 liter engine. Some mornings the truck will fire right up and other times it will crank over real slow for 4 or 5 times then start right up on the next try. When it cranks slow the lights will dim, but won't go out. I have had the battery checked along with the alternator and they are fine. Where are the grounds on the vehicle and does the starter act as a ground to the engine. Thank you