First of all, don't do it unless the sock is hand-knit or all wool!
If it's an all-wool factory-made sock, consider picking out the seam and
replacing it with grafting or a smooth darn.
I think the best darning method for socks is interlocking rows of buttonhole
stitch, which have a more knit-like "give" than woven darns.
I've posted an excerpt from Rough sewing
(which is a slightly-modified excerpt from Glove and Mitten Design for
Beginning Knitters):
http://groups.yahoo.com/group/needleworkjoy/files/Text%20Files/Darning.txt
--
Joy Beeson
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near Albany, New York, U.S.A.
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