Avoiding a metal knife when cutting an avocado can make it brown more slowly and preserve it for longer.
Most people would be happy to eat half an avocado but eat the whole thing because it's known that they brown and get bad very fast.
Here are some tips to help preserve avocado for longer:
How to cut the avocado
Metal knives are the most common ones for cutting anything including avocados. But All Recipes recommends finding an alternative for avocados.
"Metal knives, especially those that contain iron and copper, will begin the browning process faster than other knives."
All Recipes
How to preserve an open avocado
Once you've cut your avocado with a knife that isn't made of metal, how can you preserve it for longer?
One option is to rub olive oil or lemon juice on all the open parts of the avocado.
Another option is to slice an onion and store it next to the avocado in a sealed container. An alternative is to store the avocado with garlic instead of lemon.