The only sure way to know if foods are safe to eat is by measuring the internal cooking temperature of the food in the thickest part of the food. Instant read thermometers are the most effective means of measuring this temperature. The types of instant read thermometers varies greatly. You have mechanical thermometers which you can insert into the food and take a temperature, you have roasting thermometers that you can leave in the food, you can use a digital probe thermometer such as the Smartro ST 54 which has two probes with leads you can leave inserted in the food and get a constant temperature read as the food cooks, and you can use the ChefsTemp Final Touch X10 instant read digital cooking thermometer as well.