BGA Tip: You can click the cog just above your name to auto-pass close assault reactions. Maybe BGA will make this the default setting someday...
Actual tips:
1. Generally speaking Infantry can [Move 1 hex AND Battle] OR [Move 2 Hexes]. This isn't clear on the interface, and will cost you attack actions.
2. More attack actions are better.
3. More dice on those attack actions are better.
4. The goal of the game is to fully kill the requisite amount of enemy units. If an infantry unit is down to 1 guy, it's wise to retreat them into safety to deny your opponent the point.
5. Be careful of stacking your team up in one column. If you have no cards for that column, you waste turns until you do.
6. If an Armor unit can fully kill or retreat a unit in close combat, they can advance and attack again.
7. Keep in mind that if a unit has both retreat hexes occupied, any flags count as hits. This is important both when attacking and when positioning of units.