I finished the first of my dad's birthday/Christmas socks on Sunday (1/29).  I'm using the instructions from Charlene Schurch's new, excellent book, 
Sensational Knitted Socks.

The instructions are very thorough and have charts for all different sizes.  I'm using a very simple pattern, the first one in the book.  Wool:  Trekking XXL, 75% superwash wool, 25% nylon, 100 grams/2 ½ oz, 420 m/459 yds; Color: # 111 (black, grey, and yellow flecks); Needles: 2 mm (U.S. 0).
One ball of wool should be enough, although I was a little unsure.  So I had the attendant at the mail room at work weigh the completed sock and then the remaining wool.  He said they weighed exactly the same, so I hope I'll have enough to finish.    If not, I plan to undo the toe of the completed sock and finish both toes in black wool.  (Color # 111 seems to be discontinued.)