Danger! Danger!

Before you go adding indexes willy-nilly, you have to have some understanding of the data and how it is being used. Indexes do not automatically give you increased performance. In fact, in many cases, indexes can slow things down.

Is the database transaction heavy or no? Having many indexes in a database that has heavy insert/update/delete activity can really bit you, as those indexes must be maintained in parallel with the table changes.

On the other hand, if the data is relatively static, used mostly for queries, carefully crafted indexes can make a dramatic improvement in performance. Poorly crafted indexes could do little but consume space.

Another factor you must keep in mind is how the query optimizer works for the DBMS in question. Indexes need to be crafted (there's that word again) with that in mind, if they are to be effective.

Proper indexing is something of an art; it's one of those things that help keep database administrators occupied. As access patterns change indexes may need changing. I'll be bold and claim that you aren't going to find the general solution you seek. Sorry about that.