Great time of year to start the business. Instead of making yourself look like a well-established business with lots of professional signage, etc., maybe try instead to play to your comparative advantages. Let people know you're just starting out, but because of that your overhead is low (or that you bid aggressively because you want the work), you'll do the work yourself, and you've got the time to do the work promptly and properly. They'll want you to succeed. You can still assure them that you've got the experience, the insurance, and that you won't be collect a dime until they're satisfied with the work. Aim to make a fan out of every client.
I also love the idea of networking with other tree services. If nothing else, you might learn which ones are cool and which one's are not. Some overly loaded tree service might even invite you to work with them part-time until you build your own client base (much easier to do this if you don't have your own company name all over your work truck).
In my area property management companies and landlords are always looking for a deal on tree work. If you've got holes in your schedule, you might put your name out to these folks. Established landscaping companies might also be allies--they're sometimes looking for tree guys who can respond promptly to their own clients so they can move ahead with their landscaping work. Make the landscapers look good and they'll refer you again.
Watch out for the temptation to sell tree work. If you meet with a client, focus on giving them sound advice. If no tree work is critical, tell them that. Imagine saying this to a homeowner, "Although I could really use the work, I don't really advise you to do anything with your trees because...." It's a super easy way to win a fan. If they offer to pay for your advice, ask them instead to remember you when one of their friends or neighbors needs some tree work done.
