Sometimes you want a grilled cheese sandwich. Maybe it's chilly outside and you want the comfort of a warm, gooey grilled cheese dunked into fresh tomato soup. Maybe the sun is expanding and encroaching upon the Earth, and therefore it's extremely hot and all life is dead, in which case this scenario wouldn't occur, but for the sake of argument let's just say it does occur -- maybe then you want a grilled cheese. The point is, there are many times, regardless of external conditions, in which you may want a grilled cheese.
You must have a fine, sturdy bread. You must brush both sides with olive oil or butter. You must, you simply must, have a fine cheese. Ideally it's a cheese you've grated, as the many grated strands melt better than strips or blocks of cheese. You must then put the bread and cheese in a frying pan (or on a grill) and place a moderately heavy object on top and allow the sandwich to cook. You must flip. You must then enjoy. As a side note, feel free to add the following within your grated cheese and between the slices of bread: crispy fried onions, caramelized onions, jalapeno peppers, bacon, etc.
But what cheese?
I commend to you English coastal cheddar from Trader Joe's. Many people naively spend their lives eating inland cheddars, but coastal cheddars are the preferred cheddars, and Trader Joe's has one which is absolutely excellent: sharp, complex and nutty. It makes for an exquisite grilled cheese. Enjoy with a crisp ginger ale and life cannot get better.