[woodnthings]

you will want a resaw sled

Logs are big, heavy and round.... usually. You need to support the weight and keep them from turning as you saw, so a sled is the best way. There are several here:
http://www.woodworkingtalk.com/f27/resaw-sled-7552/

 

[woodnthings]

find the flattest area or make one...

You need to have a flat surface on the table to make any sort of accurate cuts. I found the easiest way is to use a power planer to quickly remove the bark and make a straight, flat area for the sled.
The first cut should be 90 degrees to the flat and by using a jig riding on the table edge you'll get a pretty straight cut. Here's the power planer in action;

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