It is a business, and in business you make money!
If you are a good player (sight reading is a plus, but reading is a must) it may be hard for you to understand why they (students) don't get it as easily as you did, or have your passion for it.
Find out what music they are into and give them work/exercises that are similar sounding.
Always make a lesson fun. Mary Had A Little Lamb is not fun. AC/DC is fun. Instead of focusing on the 400 things they are doing wrong or didn't practice, find the 1 positive to motivate them. This cultivates a passion and a steady income.
Find a beginner lesson book that you are comfortable with working out of.
Some go from really easy to quite hard for a beginner, and some stay fairly easy all the way through.
Everyone wants to learn songs right away, accommodate everything to keep them positive and interested. Bust some easy Dylan or Eagles stuff out. They have real simple versions which can be digested by beginners fairly easy. Dumb down songs they want to learn if you have to. In between strumming, you can work their single note exercises. Start out basic so they see the improvements as well.
Above all remember it is a job, and Daddy needs to get paid...