The least expensive and easiest to check go in this order:

#1 - battery connections, check out the posts for visual corrosion or white powder-looking stuff on posts.. if present clean with wire brush then a little grease and re-tighten

#2 - check batter voltage, it should read 12.4 volts at least without load, anything under then your battery is likely toast

#3 - If car is a manual check the clutch switch. You'll have to get under steering wheel and just above the clutch pedal you'll see the black micro-switch. You can check this with a ohms meter to verify that it is functioning.. if not it is very cheap and easy to replace.

#4 - key switch. This is a VERY common failure point on 986's and 996's. It is a little bit of work to do, lots of write-ups on various sites on how to replace. It is most often only the electrical portion of the switch an they run @$15... don't go for the cheap Chinese one for $7 or so as you'll get what you pay for. This switch is identical to those in Audi's so save yourself a buck or two and get one there. I got mine from Amazon.com for $12 I think earlier this year. I now keep one in my car just in case!

Other possibilities: Starter, starter solenoid, immobilizer, bad ground wire...

The ignition switch will be here tomorrow. How should I go about testing this ground?

Well....I've replace the ignition switch, starter, alternator.......still only starts with a jump. Took it in to an indy shop in the area. They said it was working fine. I drove it for about 20 miles and then went to start it. Nothing. After about 20 tries it started. It's been sitting at my house for the last few days. I'm going to take it back to the shop this weekend.