Cross-contamination
Bacteria and viruses need to be thought of as hitchhikers that can be carried around and deposited wherever contact is made. A dirty knife will deposit bacteria on freshly cooked meat. Dirty hands will deposit bacteria on the next sandwich you make. A dirty chopping board which has just had raw chicken on it will transfer those bacteria to your lettuce if you choose to use it without washing and sanitising first. The raw meat in the refrigerator is dripping juices (and bacteria) on to the food stored below. There are enormous opportunities for bacteria to move around your kitchen if we allow them to. Cross contamination is preventable and encompasses good cleaning practices, good personal hygiene practices and some organization to keep raw foods and contaminated utensils away from cooked and ready-to eat foods. No contact, No transfer of bacteria.
Preparation
Always check your food ingredients for wholesomeness before you start. The use-by-date, the look and the smell are excellent indicators that the item has not spoiled.
Don't thaw foods at room temperature. Thaw frozen food completely in the refrigerator, or in a microwave oven if cooking immediately.
Keep food clean by avoiding cross-contamination. Keep dirty preparation activities well away from clean or cooked food. Do not share utensils, plates and chopping boards between dirty operations and clean cooked food. In between handling raw and cooked foods, wash utensils such as tongs, knives and chopping boards with hot soapy water. Make sure that utensils and equipment are always clean.
Wash hands thoroughly before preparation, after going to the toilet, and after handling pets and raw food. Use soap and warm water, rubbing for at least 30 seconds.
A 10 second splash under the tap is not washing your hands.
Source: SafeFood.net.au