To prevent the guacomole from turning brown, sprinkle with lemon
juice.  If guacomole is to be consumed more than 1 hour after it is
prepared, cover with plastic wrap placed directly on the surface to
prevent it from coming in contact with the air.  

4 ripe avocados
1 small tomato, seeded and cubed
1 tablespoon lemon juice
1 tablespoon chopped cilantro
2 garlic cloves, minced
1/2 teaspoon salt
1 tablespoon minced onion

1.  Cut avocados in half all around.  Rotate 2 halves in opposite
directions to separate.  Remove and discard pits.  Scoop out avocado
into a medium bowl.  

2.  With a fork, coarsely mash avocado.  Add lemon juice, garlic,
onion, tomato, cilantro, and salt.  Mix well.