There are as many different reasons why children bite as there are solutions. A few of the things you may want to consider are:
1. Is the child teething and biting out of relief for the pain? If so the child is going to need some pain reliever and teething gel and something suitable to bite on when the need to chomp down becomes overwhelming.
2. Is the child biting as a way of getting his way/ frustration over toys. Then the environment needs to be looked at. Are there too many children in one area, can they be divided up into smaller groups? Are there ample number of favorite toys for the children to reduce fighting over a favorite toy. Is there one child who seems to be bitten more than others? Is there a way to separate the two? Sometimes a biter will try biting one child because they are passive or more assertive and fight back. The children do need to learn to socialize but getting the biting under control is a more pressing issue.
3. Is the biter lacking verbal skills and bites as a way of communicating? Work with the child on a few words or hand signals until the rest of the vocabulary comes. Even a young child can learn to put his hand up to signal Stop! when someone is invading his space.
4. Is the child imitating behavior or a game that is played at home - doggie, wrestling etc. I tried everything for weeks with a child who was biting. Finally after a month of discussion with the parents and every approach, the parents asked me if I thought the game his older sister played with him at night of crawling around after him pretending to bite him had anything to do with it!
5. Routines help children know what is going to happen next and creates a calmer environment in a toddler room. If the biting happens at certain times, maybe that time period needs to be set up differently.
In any situation, the attention should be turned to the bitee and your back placed to the biter eliminating any direct or indirect attention to the biter. You want to make sure not to give any attention to the biter not just for his sake but for the sake of any other children who decide to imitate the biting behavior.
If the situation is more than you can handle, it is always a good practice to have in your policy that the parent needs to pay for a staff person to be one on one with the child until the biting is under control or remove the child until the phase stops.
Children are too self-centered to understand being bit back (besides all the other issues of it). Biting back works because a child is fearful of getting hurt himself not because he understands it hurts others. I really wouldn't want any child of mine to ever be afraid that I would hurt him. If a child looses control and bites, he still needs to know he is a good person. I don't believe biting him back would give him that message.
M and M's may work for some children who have that level of reasoning and planning ahead but most young children bite instantaneously with little forethought.
You really need to correct the situation leading to the biting to truly control the biting. It often helps to chart what was happening in the room at the time, children, staff involved, circumstances, etc to give yourself a clear picture of what you are dealing with.