I always always toast (grill or fry) the bread. The one time I was served it not-toasted, ie just right out of the packaging, it was terrible. But they also "forgot" the mayo - this was at Dad's assisted living home and I guess they thought no mayo would make it "healthy". They also only served each person a half sandwich - granted most of the clientele were little old ladies, but Dad was over six feet tall. For all those reasons, this was the worst BLT I ever ate.
I don't make it all that often - I don't buy bread all that often - but if I do, I prefer a multigrain or a rye bread from a real bakery, toasted, add the lettuce, usually Romaine - in-season tomatoes, and the bacon. Bacon and the toast still warm when served. But, honestly, this is one of the few occasions where regular supermarket tomatoes can work anyway. It's the entire gestalt of the whole sandwich working together.
PS, Tasty - I can get behind fried bread in bacon grease, too.