Played first game tonight and was wondering if you can go below 0 on lets say a will check and then add skill bonus to bring it back up.

No, you never go below zero on a skill check. Spending a clue token on any skill check will always give you one additional die to roll.

Say, your current Luck stat is 0, and you have to make a Luck(-3) check. You can spend a clue token on this check to roll one die. If you have the Luck skill(+1 to Luck), you can roll two dice on this check when you spend a clue token.

And just as a FYI. since some new players are confused by this: the skills in the base game that give you +1 to a stat have more than one use: they add 1 to your current printed stat and let you to roll two additional dice on a skill check with that stat.

So if you get a +1 Speed skill card, it will give you 1 extra movement point per turn, add to the modifier of any Speed checks you make and let you roll two additional dice per clue token on those checks.

...and in addition to what 'zealot' has pointed out, skill checks which rely on the main stat (Horror for Will, Spell checks for Lore, etc.) also benefit from the +1 /2 rolls per clue, as well. Please correct me if I'm mistaken.

Yes, since all those are subsets of the governing skill check.

Horror checks=special Will checks

Combat checks=special Fight checks

Evade checks=special Sneak checks

Spell checks=speical Lore checks

My bad. I should be more careful when reading. The OP didn't mention anything about spending clue tokens on skill checks. At the time of posting the reply I was reading a slightly similar thread on Boardgamegeek, and got confused between the two.

When determining the number of dice to roll on a skill check you add/subtract all the modifiers to the given skill.(from game effects and cards in your possession)

Let's say you need to make a Lore(-1) check during an encounter in Arkham. Your current printed Lore is 2.

You also have in your possession a Lore skiill card(+1 Lore). There's also an environment in play that gives -2 penalty to all Lore checks made in Arkham.

The number of dice you will roll on this check is: -1+2+1-2=0. If the total number of dice is zero or less on a given skill check, you automatically fail the check, unless you spend clue tokens on it. Since you have a Lore skill card it will let your roll two additional dice per clue token you spend.

Thanks guys for the response, im glad you added the bit about the skill card cause that was going to be another question.