Think carefully about unit placement when you deploy units against specific enemy types. Archers, for instance, don't fare well against melee attacks, so a good strategy is to put them on a hilltop, away from danger but still able to join the fray.
Creative use of your units can be invaluable. For instance, if you spot your opponents sneaking under cover of a forest, set it alight and do some serious damage to their numbers.
If you find unit movement slow and unwieldy, you can speed things up using the option in the pause menu. You won't have as much time to plan your strategies, but at least there's more chance of securing victory before your train pulls into the station.