Heat oil in a skillet over medium heat
Fry corn tortillas one at a time until crisp and golden
Drain on paper towels and lightly salt
Spread refried beans on each tostada shell
Add shredded lettuce
Add cooked meat, chicken, or beans
Add diced tomatoes
Add chopped onions
Add shredded cheese
Add salsa
Add sour cream
Add avocado or guacamole
Serve immediately