To be safe with certain meats I use a meat thermometer to ensure it is done, but I do have limits to the use, for slow cooker use of more than 4 hours I do not use a thermometer, nor do I for fried chicken or hamburgers or steaks. Use your judgement on what you to measure temps on.
Here is a guide for common items:
Beef, Veal, and Lamb (pieces and whole cuts): 63 C / 145 F, which would be medium rare.
Pork (pieces and whole cuts): 71 C / 160 F.
Ground meats (I use this for meatloaf using ground beef or pork): 71 C / 160 F.
Poultry (Chicken, Duck, Turkey, whole, checked at the thickest part of the thigh without touching the bone): 82 C / 180 F.
Like I stated, I do not check temps on burgers, sausages, meat balls, pork chops or pork steaks, beef steaks, eggs, fish, fried chicken, or fried duck.