Malin Genie said:
The DCs for these sort of tasks would vary, but the '10+HD' can be considered a starting point for an 'easy' Intimidation task.
Makes sense. For most checks, however, I would try to balance it so that a highly-intimidating person has a slightly better than 50-50 chance of succeeding.
A normal check might be DC15+opponent's HD. Consider that max skill ranks=HD (or level) + 3; this means that if you had a charisma of 12-13 and max ranks in intimidate, you have exactly a 50-50 chance of intimidating someone of a level equal to your own: the DC=15+x, and you need to roll 11 + 1(cha) + x+3(max skill ranks) to succeed. (Subtract x from both sides if you want to check my math). A higher charisma tips the balance in your favor, as does any other sort of bonus.
[edited to make the equation work. Equation is this:
(DC of )15+x= (Necessary roll of) Y +1 (cha mod) + (x+3 (max ranks in intimidate))
15 + x = Y + x + 4
15= Y + 4
11=Y
where X=level of both target and intimidator
and Y=necessary roll for intimidator to succeed]
If you use something like this, consider giving plenty of circumstance bonuses and penalties. Maybe +2/-2 for every factor by which one group outnumbers the other: a party of 4 facing down a lone wizard outnumbers her four times, so the party gets a +8 on their intimidate check, whereas the same party facing down 20 kobolds gets a -10 on their check. +4 if the leader of the opposing side is killed or captured. -5 or greater penalty if the target of the attempt believes he has a secret weapon to use against the party; +5 or greater bonus if the intimidator mentions the secret weapon and explains why it won't work. You get the idea.
Finally, I'd give folks in combat the ability to intimidate their opponents by taking a standard action to do so; for this, the DC would be 20+hit dice of target. Success means opponents are shaken; success by 10 or more means opponents are panicked.
Daniel