You can't avoid injuries, which is good, but these are my strategies which work reasonably well:
- Avoid fragile players -- take durable players when possible
- Never overwork your starters -- I set a target of 220 innings and force them to the minors to miss a start when needed to enforce it
- Rest position players -- backups should start every 7 games at least
Even so, injuries still happen. That's what depth is for......