Many tradesmen don't believe in advertising online because they themselves do not spend a ton of time online however their target audience does.
If you have a website then you are probably far ahead of many people in your field as it is. If you are looking to advertise your website and get your potential customers to call you then you have a few options.
If you don't have one, get one. This will allow you to advertise your business 24/7 and give you an additional point of contact when passing out your printed materials or driving down the road with magnets or vinyl on your truck.
To get people to go to your website effectively, you have two options, spend time or spend money.
For gaining traffic to your website without cost, you will be looking at some time being spent.
Back links are very important and can arguably be the best way to increase your website exposure. Effective back links are one way links (meaning not a link exchange) from other websites to yours. For example, had you put a link to your website in your question, you would have created a back link as yahoo instantly indexes the Q&A section of their website. Even Google picks it up. You can build back links in placing your url in ads such as craigslist, creating or comenting on blogs on wordpress and myspace as well as other blogging websites. These are all methods that give you white hat back links.
Caution: do not pay for your back links through back linking companies. This is considered black hat SEO and will actually drop your ranking or get you suspended all together from the big boys of search engines.
As far as paid methods, look at pay per click as a great option. PPC is the process of advertising your business on a search engine within the sponsored results. You choose what keyword phrases you are willing to pay for being in, I.e. Website design.For cost effectiveness, consider narrowing your results as much as possible. For example, Sacramento website design instead of website design would be a more focused result and would by proxy cost much less than the broad term.
SIA Professional Services has an articles section in their website which has a ton of website marketing tips that should help you at www.siaservices./articles
Be sure you are submitting your website on a regular basis, especially whenever you are doing some good updates on your site. The search engines will see your site being updated on a regular basis and index you accordingly. There are some free submission sites, but I have seen in my experience that those don't nearly perform as well on a regular basis as professional SEO and marketing companies.
There is plenty more that you can do, but hopefully this give you a good starting point.
Good Luck and hope this helps