This one doesn't let you output the internal osc frequency/4 on OSC2, so you're pretty
limited on fine tuning the internal osc.

A somewhat easy way is to start off with 0 in OSCCAL, setup a simple loop sending serial
data to a PC terminal program, and slowly increment the value you're placing in OSCCAL
until you start receiving valid data on-screen.

I.E. serout OSCCAL = XX where XX is the value in OSCCAL while it's sending serial data to
the terminal window.

You'll start seeing vaild data for several different OSCCAL values. The one in the middle is
normally the one to go with since it gives a little room either way.

Jot down the middle OSCCAL value and manually load it into OSCCAL at power-up, or use
POKECODE @$3FF $xx where xx is the hex value to write back to the chip for the new osc
calibration value.

Most of the newer parts with 1% internal oscillators work pretty well, even for timing critical
serial applications, but don't get upset if it fails when the temperature shifts. That makes a
huge difference.