Start by cooking the bacon. I like it crispy but my husband likes it limp. So I start mine first. Don't rush it! Cook it low and slow to render the fat and crisp up the white parts. When mine is about half done, I add his. Be sure to drain it well on paper towels or coffee filters. 

Using any kind of bread (we love sourdough - and I make it alot), toast it lightly.

Spread the bread with mayonnaise then top with the avocado, then the onion, bacon and lettuce. Top with the bread.

Eat!