Is in web terms an 'FAQ'. We get asked this so very often at the shop and I usually say, 'how do you like it?' Paramount when cooking beef, but essential with other meat too. Some may prefer their lamb more pink. And there is research taking place at present regarding how rare we can stomach pork.
My advice to all of you is this: purchase a meat thermometer immediately if not sooner. These are wonderful inventions, when plunged deep into the heart of the meat (or the meatiest part) and they will give you an accurate reading as to how hot or cold your meat is. This is ideal for roasting joints. Some, even have special settings which emit an irritating beeping sound when at the optimum point i.e your 'taste requirement'. These very helpful and inexpensive bits of kitchen kit render you less stressed, satisfied and totally avoiding poisoning your Granny.
If only all areas in life were served so conscientiously on the basis of your personal preferences..