I am going out of town for about a month, and will need additional drop-ins on my 4-year-old cat. He is very friendly and chill, and loves people. In terms of what to do, the biggest things would be to make sure he has enough food and water and then to clean the liner of his litter box if it is getting full.
He also does tend to make small messes of litter, so doing some quick sweeping around his litter box would also be great!