Word of mouth. Make sure everyone you know, knows about you shop. If it's free, advertise in it. Craigs list, Facebook etc.. Always carry a stack of business cards.
Paying for advertising.
Anything in print has been a complete and utter waste for me. Less than .01 percent return. No mailers, newspapers, Welcome Wagon and even Mudlick (unless your planning on giving stuff away, which I would advise against).
What works for me (gets me 30-50 percent growth a year, just started year 5)
Affiliate with someone. NAPA, Parts Authority, FMP etc.. You need to be able to offer a decent nation wide warranty. Also it will get you on there websites and POS materials. Typically it runs 6-700 a year. Money well spent.
I offer 15 percent discount to all new customers. If your being shopped your going to have the lowest price. That will entice them to come in and try you. Going on 5 years and I still do this, although I may amend it soon if not discontinue it. Aside from this and a 10 percent military and AARP discount, I don't discount much of anything else. I don't run oil change specials etc.. I feel it brings in the wrong type of customer.
Yelp. Spend no more than $200 a month and no pay per click. Tell them that's your budget and no more. Tell them you may spend more if you see results. Yelp still brings me 20-30 new customers per month. Put the 15 percent off first time customers in your call to action for Yelp. Take care of these people. If you know they are happy don't be afraid to ask for a good review. You will live and die off internet reviews.
Google Adwords. Spent 2-300 a month the first year. Wrote my own ads and picked my own keywords. The phone would ring 3-4 times a day. When the money ran out, the phones would stop ringing. It seemed to work. I only used it the first year until I developed an internet presence.
After a year or 2 I got in with RepairPal. They are another review site with a very good online estimator. Costs about $200 a month and a couple hundred to get started. They will call you customer base and vet you. They will also ask for reviews. They got me 25 to start. That helped a lot. I probably get 6-10 phone calls a month, all that is trackable. I would say I convert most of them to appointments.
Customer Lobby. When you have a few hundred customers, you may consider them. They send out reminders and ask for reviews. They will post them to their website, your facebook page and ask for Google reviews.
Again, you can live or die by reviews. Take care of your customers. If you screw up...make it right. And, never,never lie. Just be tactful and straight up.
Grand opening. Never had one. Always though the time, energy and money would be better spent someplace else.
You may consider openbay.com. Got a call from them the other day. Sounds interesting. Not sure if it will take off or not. Nothing ventured, nothing gained.
Good Luck!