Most lead-based paint poisoning in children occurs by exposure to lead dust, and testing dust will determine if you have a lead hazard you have to deal with. The test kits, available at home centers and hardware stores, include step-by-step instructions for collecting the samples, bags for the samples, plastic gloves and an envelope to send the samples to an EPA-certified lab for analysis. Results, mailed back in about two weeks, will tell if the samples contained a potentially harmful level of lead dust. If you have a dust hazard, contact your local health department for remediation guidelines.
However, before remodeling or otherwise disturbing painted surfaces, it's best to have a professional lead inspection and risk assessment done. This will tell if your home has lead-based paint, where it's located and if it's hazardous. Keep in mind that lead paint itself is not necessarily hazardous, especially if the surface is in good condition and the paint isn't flaking or being worn down (along sliding windows, for example). Find certified inspection firms through your state health department or the Environmental Protection Agency.
Don't be discouraged if you have lead paint. You can handle it safely. Follow the guidelines online at epa.gov/lead or call your local health department.