Traditionally, hitters in a particular spot in the batting order are expected to fill certain roles. If you’re building a batting order based on old-school thinking, you’ll want your leadoff hitter to be fast enough to bother opposing teams on the bases, while your No. 2 hitter should make contact and be able to move that leadoff hitter along. The best hitter on the team bats third, and the best power hitter fourth. Another power hitter bats fifth. The rest of the lineup falls in descending order, with the last hitter being the worst.
Optimized for Offense
As more advanced statistics have become common, new strategies for lineup optimization have developed. In this approach, your leadoff hitter should be the hitter who gets on base the most, since that’s who will get the most chances to bat. Your No. 2 hitter would be the second-best at getting on base. The third batter should also be an on-base specialist, with your No. 4 hitter being the best hitter on the team with power. No. 5 should also be a power hitter. No. 6 through No. 9 generally should be placed in order from best to worst batters, but speedy hitters should bat before slower ones to maximize your team's run potential, all else being equal.
Focus on Fairness
If you’re making a batting order for a Little League team, or a series of casual softball games, you may be concerned less with maximizing your scoring potential than for treating everyone relatively equally. One way of doing this is to divide the lineup into thirds. Anyone who hits in the top three slots in the batting order one week moves to the middle third of the lineup for the next game, and then hits towards the end the following week. Within this structure, you’ll still want to adjust the specifics of who hits where. For example, if you have hitters who are still afraid of the ball, don't lump them all together in the batting order, or your better hitters will be stranded on the base paths when that part of the order comes up.
Know Your Team
The best batting order for your team depends on the quality of your hitters, and how you’ll most likely score runs. If your team has strong pitching but not much power, for example, every run will be precious. In that case, you might want to have your No. 3 hitter be good at bunting, so when your first two batters reach base safely, he can sacrifice them into scoring position.