I have attached examples of how I do them. We use them for accountability, and for troubleshooting ("why is it THIS value???"). I have a mechanism embedded that allows you to turn on and off auditing by table. We use this method for any internally-developed databases. They are used by only a few in each department, so it won't be overwhelming the database to do it this way.

If you are doing hundreds or thousands of transactions a minute, then I would look for a different way of doing it.

Hope it helps (and I hope my attachments attached).