A's have ranged attacks (Archers?). You and the G enemies (melee-only) have health progression from blue (lowest), green, red, to purple (highest I've seen). The D on the right is your remaining arrows and follows the same progression scheme. Yellow symbols (except for the stairs) are items/power-ups (be careful because the Archers will shoot over them). q for ammo (quiver?), p is a life-up (power?), l hurts all the enemies on your line.
The only decision that you can ever make is whether you want to shoot or not, so just look at the lines that have ammo and figure out if you want to shoot that turn or move forward.