column indexing strategy

[Michael Corr]

Hi,
I'm trying to figure out the best strategy for indexing columns in a table. Is it better to index a column that is often found in the SELECT part of a query or the WHERE part?

For example:
SELECT col1 FROM table WHERE col2=x;

Is it more important/effective to INDEX (col1) or INDEX (col2) when I create the table?

thanks,
Michael