In the abstract, I know this sounds easy. But, in the actual practice it's not.
John, what do you do if you have two employees both making $12.00 an hour. Forgetting the percentage rule above, say you give one a bonus of $300 and the other a bonus of $200.
1. Do you make it well known to all that they are not to discuss their bonus amount?
2. If they do (and they likely will), do you do anything about that?
3. Which brings up the real issue, how do you handle the resentment that will ultimately occur?