First thing to do is describe your attack.
"I swing my greatsword around in a huge arc, hitting all targets within 2 squares of me and knocking them back!"
Next we break this down into numbers.
Greatswords deal 2d6 base damage. All targets within 2 would be an AoE2 effect. and Knockback 2 seems like a good effect to add to it.
Put these numbers into the template.
2d6=2 points, AoE 2=1.5 points. Knockback 2=0.5 points.
Add them together, and you have your Stamina cost of 4 for this attack. But what if the attack comes out to be an odd number of Stamina? You can use other effects to balance out, raise, or lower the cost. Taking a -2 Accuracy penalty to the attack could give me 0.5 more points to work with, or making an attack Limited.
Want a giant attack with a lot of BANG? Let's try a new Charge Attack. Charge attacks add an element of time and strategy. If you do a big attack that says "Charge 5," that means that it will go off in 5 turns. (or 5 cards on the initiative deck.) You will have to watch out, though - you're susceptible to attacks while charging, or your enemy might be lucky, have his turn come up first, and be able to escape. On the plus side, Charge Attacks lower the stamina cost of your big risky moves considerably, allowing you to pull off impressive feats, like this one for Heavy Blunt Weapons (such as great clubs):
Slugger
6 Stamina Charge 4
Limited
Requires 13 Physique
Wind up one massive attack to send your target airborne. Deals 3d12 damage and knocks the target up to 6 squares away.
The higher the stat requirement for a maneuver, the more points you'll have to work with, as well. You luckily don't have to worry about the math too much, as our development tools will do the work for you!