Legacy database tricks and techniques

I have been looking for a "definitive" guide to legacy database
support for Rails and I am coming up relatively empty. There are a few
tips and tricks out there but no specific step by step guide for
integrating rails (Activerecord) with legacy schemas. Anybody seen a
good one and can post a link?

I have a legacy DB where table name pluralization isn't an option
(easily fixed) and where table names follow absolutely no convention
whatsoever, where primary keys are rarely, if ever, a sequentially
assigned numeric field. Primary key values are usually user assigned
values rather than auto incremented values and they can be both
numeric and character. Some tables have compound keys.

I have seen all of these addressed in specific, separate ways but I
haven't found anything that deals with all the possible issues
implementing Rails in a legacy world.