How do I prevent udon noodles from sticking together & turning into a gluey glob when I boil them?

The above techs are good.

But sometime you just don't want to dirty and clean big pot for small portions.
I fall back on another tech. Told to me by a Japaneese housewife.
Normal sized pot and just a serving of two of noodles. (which what I normally make).

Salt the water and bring to boil. Add noodles and stir immediately.
As it starts to boil over....add a cup of water. Wait...until it starts to boil over again.
repeat that three times while stirring with chopsticks. Watch it..as it will boil over..thus the addition of cooler water.

and then rinse well!

I agree with EmilyC a large pot, lots of boiling water (make sure its a rolling boil) and stirring frequently.

There may be better tricks out there, but I make sure to use plenty of water (about 6 quarts for 1 pound) and stir frequently to prevent them from sticking.