1)Google Local: If you don’t already have one Create an account on Google Local. Enter your company name, address, phone number and website. Verify the information with a postacard or telephone call. In a few weeks you will help you get a map listing for your company name or industry and town.
2)Google Coupons: Coupons are a great way to bring new customers into your business or remind old customers that you’re still around. Google has a free coupon tool that puts your coupon on relevant local searches.
3)Google Base: Google base is part of Google’s one box service. Google uses it to try giving the most appropriate answer from different data sources. If you are selling products you can upload feeds automatically into Google Base and often get preferential placement. You can also upload your business, or special event.
4)Yahoo Local: Yahoo local is a directory organized by category and geographic location. You can get a basic listing in Yahoo Local for free. People searching for your business or industry can find your listing
5)Get Reviews: An integral part of the Yahoo Local listings are reviews. Ask your good customers to write reviews for you on Yahoo local. Businesses with higher ratings will get preferential listings.
6)Press Releases: Doing something newsworthy? If you are you can always submit a press release for free at PRLeap.com. Be sure to check out their tips like 25 Action Words for Writing a Newsworthy Headline and Why Localizing a Press Release to a ZIP Code and City Matters.

It is very easy to promote established business. but to promote any small business like real estate, etc.. it is difficult task. but i think, internet is the best place to promote any type of business.

1.Get listed
This is one of the most basic methods of business promotion. List yourself in as many business directories, yellow pages, and local business Websites as you can find. Many of these will list your company for free, though some might require you to pay a small fee. This type of promotion is well worth the time and investment, as most people consult these publications when looking for a designer, plumber, electrician etc. You see the point.
2. Contacts
It's not what you know, it's who you know. This little phrase holds a great deal of water in the small-scale Web design industry. When you're first starting out, you'll find that a lot of your work comes in via word of mouth promotion. It's therefore very important to make connections early. Do a few free sites for local charities, community groups and organisations - this is a great way to build up your portfolio and also spread your name around potential client firms. Eventually you'll be approached by 'a friend of a friend of so-and-so' who wants a site designed. This is an example of 'viral marketing' and is one of the most effective methods you can use to promote any business.