Jamil Zanischeff has a great yeast pitching calculator over at his Mr. Malty website. As a general rule of thumb, I pitch 2 packets/vials of yeast for most of my beers between OG: 1.030 to 1.050, 3 packets/vials for 1.051 to 1.080 and 4 packets/vials for high gravity beers over 1.081.
You can just create a yeast starter and time it to pitch while the yeast peaks in it's growth phase (usually 24-36 hours before your brew day). Or, wait until it ferments out completely, decant off the water (pour it out carefully) from the yeast cake, and pitch the remaining slurry.
Good aeration and yeast nutes can also help, especially in high gravity worts.
Glad your yeast is finally doing it's thing.