If you've been contaminated with hazardous materials, you'll greatly improve their chances of survival by conducting personal decontamination. In most cases, taking off your clothes will remove 80-90% of the potential contamination. Then wash yourself with water (or soap and water if possible).
Scraping (with a piece of wood, for example) can remove bulk agent by physical means. Washing the skin with water or a water/soap solution will physically remove or sufficiently dilute most contamination. Be sure to scrub well (using a stiff brush, if possible).
These can be used to reduce the quantity of chemical agent available for uptake through the skin. In emergency situations, dry powder such as flour, detergents or even soil may be useful. Flour followed by wiping with wet tissue paper is reported to be effective against the nerve agents soman, VX, and mustard gas.
These are effective in the decontamination of skin or other materials. Disinfectants such as bleach or Lysol spray or Clorox (which contain chlorine) will destroy most biological agents and are effective against the blistering agents. For biological agent exposure, you'll need to scrub yourself well with a chlorine solution for about 15 minutes. In the case of blistering agents, about 5 minutes should be enough.
Be sure to dilute the solution in water before you use it on your skin and rinse the solution thoroughly off your skin after use. You should use a 5% solution to decontaminate equipment and objects and a 0.5% solution to decontaminate your skin. A 5% solution is, for example, Clorox straight out of the bottle. A 0.5% solution is one part Clorox with 9/10 parts water.
NEVER decontaminate you face using hypoclorite solutions. Wash instead with soap and water. If possible, use an absorbent powder with wet tissue (as described above).
Chlorine is also available in tablet form. The tablets have the advantage of being easy to transport and store, and they have a longer shelf-life than liquid chlorine. Ordinary laundry detergent with real chlorine bleach (as opposed to the non-chlorine type) is very effective against most agents.
Decontamination is an initial reaction to exposure. Once decontaminated, you should seek immediate medical attention.
There are some products available that can help you in the event of contamination or exposure.
Prepare a decontamination kit to include in your safe room with your emergency survival kit. The decontamination kit should include Clorox (or equivalent chlorine-based bleach), scrubbing brush(es), soap, damp swipes, plastic bin liners (to isolate contaminated clothing or materials), a change of clothing, detergent, tissues or cloths (to wipe surfaces) and an aerosol to spray surfaces (a used spray container like those used for window cleaners would be enough).
You can find many links online which explains in great detail how you can decontaminate yourself after a chemical or biological attack....just look it up, practice, practice, practice.