Using a 7812 you will have to use a heat sink...
or spread the disipation across more devices...
An old trick to boost the current output of a regulator circuit...
The regulation isn't so tight, but it's so simple.
As the load current from the regulator approaches 1 amp,
the drop across the resistor is enough to start turning on the transistor.
___________________________ _______________
| C\ PNP /E |
| \ / |
| __________ \_____/ |
| | \ | |
| | 1 AMP \ | |
----| REGULATOR >---------------\/\/\--+
| / | 0R5
|__________/ ------- 0.5 ohms
| _____
| / ¦ \
| |
|------------- 1uF
|