We can't completely control the amount of metals that enter our bodies, but doing things like drinking filtered water, eating organic food, wild fish (instead of farm-raised) and not getting dental amalgams--or having them removed (by a metal-literate dentist of course--very, very important!)-- can help keep body levels down.
Being infected with Lyme disease presents a special problem when it comes to heavy metal toxicity, as Bb and Company are thought to sequester metals. When they die, they release these metals into the body. Thus, a person who tries to fix their metal problem before treating for Lyme will make incomplete progress. Add to this the fact that metal chelation can take years.
Finally, Lyme disease sufferers tend to have detoxification problems, and are likely to accumulate and retain metals at a greater rate than a person with fewer health problems.
Metal chelation is an art unto itself, and if done improperly can re-distribute metals into the body, causing more problems than if the metals had just been left alone.
Much controversy exists over what constitutes a safe, effective chelation method.
Chlorella and cilantro are used by many, but these are thought to form imperfect bonds with mercury, hence allowing for the possibility of re-distribution in the cells if they are "dropped" by the chelator on the way out of the body. Chlorella at least, is generally thought to be safe, however, and these are a relatively inexpensive option for chelation. Bear in mind, though, that cilantro mobilizes more toxins than it can carry out of the body and should be taken simultaneously with chlorella, so that the chlorella is there to mop up the excess. Cilantro is also thought to be contaminated, but by boiling it into a tea, these toxins can be removed.
DMSA with Alpa-lipoic acid is thought by some experts to be a better option for chelation, as these form stronger bonds with metals and are thereby safer. The drawback to DMSA is that it must be taken on a regular schedule, every four hours or so, even during the night. It can also produce side effects.
Finally, PCA-rx by Maxam Labs is a spray that removes metals via clathration therapy, meaning, the toxin is completely encapsulated by the chelating agent, thereby preventing it from being "dropped" on the way out of the body. For this reason, it's thought to be highly safe as well as quite effective. The only drawback to this product is its price; $125 a bottle, which may only last a month.
Other chelation methods exist, such as glutathione, but for the sake of space I mention those most commonly in use at present.