Like evil said, do a top command.
% top
This will list the top processes running (the process id is the left most column). If you want to boost a process in priority, do a renice on it and set it to a value below zero (-20 is the lowest and zero is the default setting of all processes). Like this:
% sudo renice -20 378
This would set the priority of process 378 to the highest priority. You need to do this as root (sudo).
To lower the priority, renice the process to a value higher than zero (again, twenty is the limit). Like this:
% renice 12 452
You do not need to be root to lower a priority. This set the priority of process 452 to the lower priority of 12.
Taft