Keith is an IT professional and how he got into the business is through ITDRC.org. It's a group of IT pros who deploy in the event of national disaster. That's a great way to get started and develop serious experience and serve the community at the same time. Leo says that HAMs have been doing that for a century with radio. So it makes sense that computer technology would follow suit.
Small businesses can't usually afford an IT pro as well, so getting affiliated with a small business and helping them to network is very helpful and a good way to get started.