One way to attract traffic to your site is to make sure that you are listed in search engines. Many users search for information, so they may find your site.
However, search engine listings are not helpful for all sites, and it is more or less impossible to get a top-10 result for most single-word keywords, never mind the really popular ones like 'sex' or 'mp3'.
Submitting to search engines
You could check the most popular search engines and make sure your site is included. For example, check that you can find your site in Google. (Google is a popular search engine which also powers Yahoo's web search.) Search for some text which is unique to your site, like the site name.
Some search engines have a 'submit your site' option which you can use if the site is not listed. It is probably worth doing this, but only for the major engines - don't waste your time with the others. Avoid any services which claim to submit your site to hundreds of search engines, whether these are free or involve a fee. These will not benefit your site, and such 'spammed' submissions are ignored by most listings services. (In other words, it's basically a scam.)
Achieving good results
If you want your site to be ranked high on search results from the search engines, the first step is to consider keywords you would like to aim for. You need to be selective here: on the one hand, you have zero chance of getting a good rating for most single keywords, but on the other hand, there isn't much point being #1 on a search for powered mobile combat suits with beam cannon because nobody is ever going to type that in to a search engine.
Once you have decided on some target keywords, you can design a page of your site (generally the front page) accordingly. Include the keywords in:
- the <title> tag
- headings (<h1> etc.)
- normal text of the page
- the META keywords tag (see other references for information)
Do not include keywords many times in a row, or otherwise try to 'fool' the search engines. They already thought of that, and your site will actually be penalised for it. It is best if you include your keywords as part of the natural text of the site, writing text so that it includes the keywords.
Google and other engines determine search relevance from links to your site as well as the content of your site. In other words, if popular sites link to yours, then your search rating is boosted.
Obviously, links from popular sites can also benefit you directly.
If you are developing a site for a particular topic, try to find appropriate, popular link lists that cover that topic. For example, if your site is about knitting, there may be some other knitting sites which contain links. If so, and if your site is good quality so that they might be willing to add a link, you could request that your site is added to the list.
Necessary or not?
Many sites do not benefit from search engine positioning. For instance, there is little point (nor chance) of a small local estate agent which only handles one area of one country getting the #1 result for 'estate agement'.
If your site is locally related, don't worry about search engine placement except possibly with locality keywords (for example, you might go for 'Milton Keynes estate agent').
Whatever your site, you should try to make sure that it does come up in search results if people type its actual name, in case people who already know about your site are trying to find it.
(Incidentally, an entertaining diversion is to search for people's real names in Google and see how highly they rank...)
Not sufficient if you really want traffic
If you really want to have traffic on your site, search engines are not the only answer. Your chance of getting significant traffic to a new site from search engines alone is very, very slim.
Reference: Search Engine Watch
The excellent Search Engine Watch provides more detailed information on search engines, including charts of the most popular engines, and tips for achieving high placement.