Hi Michael,
Nice to have u in this forum. Perhaps it is almost impossible to list all criteria for a good keris. It is subjective and u have to define your own standards. I think what u need to do is:
1. Avoid buying anything first. At least you had to spend 2 months studying first. Study the standard text (which nechesh had pointed out). It would be helpful if u can read malay or indonesian as since some good literature such as Harsrinuksmo's Ensiklopedi Keris is written in Indonesian.
2. Look at ebay kerisses everyday using all searchword
and comparing prices,
3. Get to know people who are really involved in this for quite some time, find fellow colectors around etc.
4. Handle or at least look at keris pictures (lots of it)
5. Finally, set an objective on what u want to achieve in collecting. If u dont set this, u may found yourself with lots (LOTS) of kerisses in the end of the day.
Theres some javaneese keris yahoo groups available. Perhaps u can meet some people through the groups. If u directly goes to the market and buy it, the probability of u got a fake is quite high. To me, keeping a few very good ones is better than having hundreds of average ones. Expensive ones does not mean good ones. (Depending on your objective and pre-selected criteria) Well, i'm not so great in this, but i think this can be used as a general rule.
Good luck,
Rasdan