Talk to a tax accountant now - before you take any stock/options. You need to understand the tax and cash flow consequences of options. If you don't plan this right, you can wind up with a huge tax bill and no money to pay it with. To make things worse, if the stock then goes to zero, you'll still have to pay the taxes, even though you never saw a cent.

Negotiate vesting. Negotiate triggers (what happens if you get acquired/fired/relocated). Negotiate the length of time you have to exercise options after you no longer work there.

As for how much? As much as you can get. It's that simple.