1. After some probation period, fire only as a last resort or for really terrible behaviour. Have a plan to correct behavior in all other cases.
2. No layoffs unless the firm's very existence is threatened. It's a tough year? Too bad, that's part of the risk involved in being the owner.
3. Keep pay up to market/replacement rates. If someone is 20% more valuable with his new knowledge, pay him 20% more. 4. Have good benefits/vacation policies.
5. Make sure there's lots of interesting and challenging work to do. Allow people to switch roles/teams on a regular basis if they're interested.
6. Hire good people.
That's a company I'd be loyal to, and I think a lot of others would be too. Sure, you'd get people who would leave for their own thing, or a dream job, or because their husband/wife got a job 2000 miles away, but I don't think you'd see people jump ship nearly as often.
The other stupid thing is companies trot out how much it costs to hire a new person, but never want to invest in just retaining their employees.
In this day and age, anyone who expects loyalty--from an employer or an employee--is either blinded by nostalgia, hopelessly naive, or a blithering idiot. Loyalty in the workplace died many, many years ago.