Do your learn them as separate skills and with separate weapon tables?
In my games:
As separate skills: Yes. I had them listed as Spear w/Shield and Spear 2-Handed. As Cory posted, I also treated a spear w/shield as a "short spear" usually 5 to 6 feet total length, and spear 2-handed as being a "long spear" usually 6+ feet total length. Furthermore, I also allowed the players to learn using a Spear w/Shield and Shield Bash as a Two Weapon Combo skill so they could use both in the same round. Otherwise, they could only use the spear
OR shield bash in a round.
Separate Weapon Tables: No. I always used Spear attack table with all crits being Puncture. However, a spear with sufficiently long blade could conceivably be used with Slash crits (if sweeping with the spear). But that, IMHO, would only apply to the Spear 2-Handed skill. Spear with shield would always be puncture since the attacks would always be thrusts.
rmfr