I do my lineups in two ways . . .
Up to the All-Star game, my lineups are set by ratings, or by last season's stats, or a combination of both. Whatever "feels" right to me. Either way, it's pretty much set for the first 91 games.
After the All-Star game, my lineups are set by stats; specifically by splits. I feel that by that time, I have a significant enough sample size to make some choices based on stats, and will tinker with my lineup accordingly. The deeper we get into the season, the closer the stats should normalize to where they belong, and guys will naturally fall into place. But if a guy has drastically overperformed in the first half, and continues to overperform in the second half, he'll stay in the heart of the lineup and I'll try to take advantage of what I know is just a random statistical anomoly. Likewise with an underperformer. He'll stay in the lineup, but may be dropped to the seven or eight hole until he earns his way out of there.