Your question is far to general. We need specifics. We can't supply a good answer if we don't know anything about your project or the requirements. Also, we won't do all the work for you. You need to tell us what you have done so far and what specifically you are stuck on.
If you're not even sure where to start, you should try
google[
^] for ideas. I looked at the first few links and they have a few different audit trail methods. One guy just tacks on a couple of columns to each table to track who and when it was updated. Another has a seperate table to track all changes. It all depends on how in depth your audit trail needs to be.
There is even a Code Project article in those google results...
Audit Trail – Tracing Data Changes in Database[
^]
Hope this helps.
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