The affix calculator here is useful:
http://www.diabloii.nu/affixcalc/
It's generally considered best to use an item just good enough to be able to get the affixes you want
I prefer grand charms from the end of Act 2 NM onwards (ilvl 50 enables skills) and small charms from the end of NM onwards (ilvl 61 enables of Vita and of Good Luck). Ruvunal is quite right about the high level elemental damage affixes - to some extent it is a matter of personal taste with regard to what you are looking for
I have also spent some time looking for a small charm from Hell Nilathak - potentially a 450 poison damage small charm ;)
I think cubing charms is very strong both for twinked characters and for no twink characters and that it is the most effective use of perfect gems
You can check monster levels (which tells you the ilvl of things they drop) on Spirea's site, hosted here and accessible from the front page
http://www.diabloii.nu/affixcalc/
It's generally considered best to use an item just good enough to be able to get the affixes you want
I prefer grand charms from the end of Act 2 NM onwards (ilvl 50 enables skills) and small charms from the end of NM onwards (ilvl 61 enables of Vita and of Good Luck). Ruvunal is quite right about the high level elemental damage affixes - to some extent it is a matter of personal taste with regard to what you are looking for
I have also spent some time looking for a small charm from Hell Nilathak - potentially a 450 poison damage small charm ;)
I think cubing charms is very strong both for twinked characters and for no twink characters and that it is the most effective use of perfect gems
You can check monster levels (which tells you the ilvl of things they drop) on Spirea's site, hosted here and accessible from the front page