i'll fill them all in until there are no more obvious possibilities. then out of all the ones that are left with two possibilities, i will consider the number that there are least of in the whole grid. then i'll try that one and see how much impact it has on the rest of the table - e.g. how many extra new possibilities there are etc - then i will try the one which has the maximum impact on the rest of the table. it is pretty crude, but i haven't really thought about it much. in fact i have written an excel program for my dad which demonstrates this:

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=5994788241&ssPageName=ADME:B:LC:UK:1

if anyone is interested in it. it is really an under-construction tool to help explore your advanced strategies to find the most efficient methods of solving them.