Cook bacon in a heavy-bottomed frying pan over medium heat until crisp. Drain on a plate covered with paper towels.
Wash and slice tomatoes.
Separate several leaves from the head of lettuce, rinse them and pat them dry with paper towels.
Toast the bread and spread one side of each slice with mayo or ranch dressing.
Assemble sandwiches by layering bacon, lettuce, and tomato slices between 2 slices of bread.