I'm not a "lawn guy" but do social marketing.. Some advice for Facebook:
- Make sure you have a "Facebook Page". It's different than a Facebook Account. Your customers can like your Page without being friends with you, so all your customers won't be having each other seeing each others things.
- Post to that page useful information throughout the year that pertains to your area. If you just cut the grass and customers fertilize, remind them. Whatever it might be.
- When you do a really great job on a really great lawn, post a photo. Obviously you'd have to either get permission or be sure it's just the grass and not recognizable by anyone where it would be. In essence you'd be creating a social portfolio so when people do find your page they'll be like wow this guy is good.
- You could also give a discount to customers if they mention you on Facebook. Maybe a one time you mention us to your friends and we give you a discount for one cut. Customers can type @(your page name) into their status update and it'll show up on your Facebook Page as a mention, and all *their* friends will see them talking about you.
And the biggest one of all: Don't go social if you do a bad job, it'll backfire real quick =P Post an update once a week and don't use automated software to do it for you and it can be the best "free" advertising you can get. I shopped for my Septic System, Oil Delivery, everything through FB pages..