sdt said:
1. What is regeneration supposed to look like? When you hit a troll with a normal sword does it cut normally or does it rebound off?
Depends on the creature. It's important that your players know what's going on, and that regeneration doesn't look like Damage Resistance, so they can tell the two apart.
Remember that regeneration changes all damage except those from a particular type into non-lethal damage. For trolls, it's fire and acid.
So, a normal sword hit actually hits the troll and cuts it, but the body basically sews itself up behind the blade. There's a limit to how much a troll's body can cope with, however, and it's possible to beat the troll up faster than it can completely heal itself. Thus, you can knock a troll out with normal weapons. I generally describe it as the troll being comatose, but with the wounds still slowly stitching together, with the arms and legs still twitching.
Any fire or acid damage has a readily visible effect - the part that's damaged doesn't grow back as quickly and, eventually, it doesn't grow back at all.
2. If I hit a troll with a flaming sword is all the damage dealt considered fire or only the d6 flame damage?
Just the 1d6 fire damage is actual fire damage. Everything else is slashing (or whatever the weapon is).