The Power Gauge is an essential asset to a fight. The rise of the Power Gauge is always the same, but the amount it needs to gain upon gaining a stock is determined by the Tactical Order chosen. When the Power Gauge gains a stock, you are able to perform a DM. When the Power Gauge gains two stocks, you are able to perform a SDM.

Performing special moves will raise the Power Gauge. If that move connects (hits or blocked) with the opponent, it will raise higher. Multi-hitting moves, whether it be 2 hitters or anything, will raise the gauge each hit connected with the opponent. Throws, command moves and normal attacks raise the Power Gauge, but to a lower extent. Command moves and normal attacks that are multi-hitting also raise the Power Gauge on every hit connected.

Performing a DM depletes one stock while performing a SDM depletes two stocks. Whether the DM / SDM hits or not the respective stock still is depleted. However, if the DM / SDM hits the opponent, the gauge will raise.
 

Aside from being able to perform DMs and SDMs, the Power Gauge has more uses. A Striker call now depletes one stock from the Power Gauge.
 

When being chipped near death, it is always useful to perform a Guard Break command. Guard Break command is performed by pressing C + D during blocking an attack. Another alternative would be a Guard Roll. A Guard Roll is performed by pressing A + B + f/b during blocking an attack.