C210 pilot experiences engine failure at 5;000 FT due to fuel exhaustion from the right tank. After declaring an emergency and switching fuel tanks the engine restarts and the reporter continues to a normal landing.

Narrative

Upon descent from 8;000 FT to assigned level of 4;000 FT my engine stopped running (at about 5;000 FT) due to fuel exhaustion. I declared an emergency with ATC and switched fuel tanks from 'RIGHT' tank to 'LEFT' tank using the boost pump switch. The engine immediately restarted. ATC was giving me vectors for an emergency landing when I notified them that I had restarted my engine and was able to continue my approach to landing. I also explained my error to the Controller and apologized for my error. (I should mention that the Controller really did a great job of immediately providing emergency support guidance). I continued with a visual approach and landed. The engine had stopped running because I had failed to manage fuel properly. When I departed; my fuel selector switch was in the 'BOTH' position. Shortly after; I switched to 'RIGHT' tank position to compensate for the fact that the plane always draws heavily off the left tank. My intent was to switch back to 'BOTH' after an hour. I failed to make the switch and exhausted the available fuel from the right tank. Total time that engine was not running was about 15 seconds. Normally; I fly with the fuel selector switch on 'BOTH' and only switch to 'RIGHT' to even the weight when the gauges indicate that the left tank is much lower in fuel than the right. This day I thought I was being proactive and then by not properly monitoring the gauges exhausted the right tank.