I just made a little log cabin quilt. I pressed all the block seams away from the center. When I sew the blocks into a row, I press each row in opposite directions, because I like to match my seams by nesting the seam allowances together. But when the rows get sewn together, I press that seam open.
Stitch in the ditch is harder to do than most other types of quilting. If the logs are small, you could stitch down the middle of each log, working in a square spiral as you go out. If the logs are bigger, you could stitch about 1/8" to 1/4" away from each seam. Or maybe echo the outline of the dark sides separately from the light sides.