1. You want your own domain. (My domain is $120/year -- dreamhost.com)
2. You want to showcase your work on it.
3. Get listed on google local business. (You need a web page as destination.
4. Once you get a client, ask if you can post a sign on their lawn for 3-4 days a month. Give them a discount any time the sign is there. Sandwich board: "Another fine yard job by Acme Landscaping -- logo, phone number. Make sure the phone number is readable from a moving car.
5. A month after you get a client, run a flyer saying "Notice the yard a 1234 26th street? The pink house with the big elm? You could have that look too. Contact info. Drop a flyer in each mailbox that is a reasonable drive by for that address. Do these up on your printer at home.
6. Reserve Saturdays for commercial accounts. I hate waking to mowers in my neighborhood on my day off. If you work Saturday residential do jobs that don't require an engine. This is also a good time to spread your flyers. A lot of time you will catch people home and can chat them up.
7. Here Kijiji is big on small business advertising. The listing is free. And you can write it up in different ways.
8. Don't be tempted by the Groupon type marketing. These are die hard bargain hunters and you will get used and dropped.
I have yet to get any business through yellow pages, or their allied directories. Get the free listing for online places though.