In reply to jon342:
I always use thin Bridgedale liner socks winter and summer under my main socks.
I knew someone who had bad blisters. They used one pair of quite rough thick socks, which had rubbed.
Of course, some people will say that they just wear one pair of thick socks and they've never had any blisters - but liners are best for me.
However make sure these don't make your boots tight. If so, reduce the thickness of your outer socks.