the only answer i could give would be to do top quality work. i do the very best job i can do. i have customers who have been with me for years. that is the way to keep residential customers. commerical jobs, goes to low bidder more times than not.
The first year I did this I worried about losing cust. over the winter, so in Febuary I sent out flyers about spring cleaning and didn`t get but 1 call on this from my customers. At end of febuary I was really worried and in march I went out and checked out the lawns to start work, when I arrived at first house the customer comes out and told me they really liked my flyer and figured I would start when I thought it was the right time,wow. I talked to 4 more that day and they told me the same thing, now the only customers that I loose are the ones that I pick up during the season and are slow payers,or won`t pay for the work that they expect.
Do top QUALITY work and treat them as a friend as opposed to only a customer. I send out birthday cards and Christmas cards. Treat them right and you will have a customer for life. Just seems to work for me.