I just changed my coolant as well. Here's how I emptied my reservoir.
Have the drain pan, or other container that you want the old coolant in near by.
Remove the hose near the left of the rad cap, this is the hose that goes to the reservoir. Direct it to your drain pan.
If you have compressed air available, great. If not, I used the 'blow' option on my dad's shop-vac.
Cover the lid of the reservoir with a rag, and insert the air nozzle, or the vacuum hose end. Pressurise the reservor, the coolant will now flow out of the hose that was disconnected. I know it would be much faster with compressed air, but I didn't have any available at the time. It was a little slow with the shop vac, but it got the job done. Not much pressure, but enough was there to force it all out.
Re-install the hose, and fill the reservoir accordingly.
Hope that helps
Matt 8)