Ignore spam and websites that offer to submit your website to hundreds of search engines. At best these are wastes of time or money and at worst they can hurt your ranking.
Rather than focusing on a single word, try adding a few words to make a keyword phrase. You may want to read about effective Google searches to see how keyword phrases help with searches. If you were searching for your own website, what keyword phrase would you type into Google for each page? Would you look for super fast widgets? Would you look for cooking with widgets? It may be helpful to get a different perspective. Ask someone else to read your page and suggest what they think your keyword phrase might be. You can also check Google Trends to see if one phrase is starting to gain popularity.
Try to stick to one subject per page, and stick to one keyword phrase per page. That doesn't mean you should write stilted text or use odd phrases. Clear writing is both easier to search and easier to read.
One of the things Google looks for when it catalogs pages is the density of the keyword usage. In other words, how often the keyword occurs. Use natural phrasing. Don't try to trick the search engine by repeating the same word over and over or making text "invisible." It doesn't work. In fact, some of that behavior even get your website banned. Read more: Google Dont's - Bad Tips and Dirty Tricks That Will Get You Banned.
Give a strong opening paragraph. Google may or may not search beyond the first 200 words or so of your web site, but it definitely looks at the first paragraph for keyword density.
You can check your keyword density with Google Toolbar.
Name Your Pages
Give your pages a descriptive name with the