Well i think that you should do, as the big captain says and run some steel wire thru it at about 200C
Also a good tip is to never have the extruder heated for more than 5 minutes without making at least 20mm extrusion. Even though most firmwares (from what i know) keeps feeding a little filament all the time, it isnt enough to prevent a clog.
If your extruder have stripped the filament, then you should clean the hobbed bolt with a toothbrush. Another thing you can do is attach a head from a toothbrush to the extruder so that it brushes the extruder clean all the time (see my upgrade thread in the solidoodle forum)
And lastly attach a filament cleaner (sponge wrapped around the filament at some point near the extruder)

I hope that helps