In some search engines, it can be a month or more before even your first page is indexed, and much longer before your site is fully indexed. That's because most search engine crawlers typically retrieve only a few pages from each site on each visit, and visits can be weeks apart. Since it can take months for your site to be fully indexed, you should have your pages online months before you expect people to search for what's on them. So if you want consumers to find your site when they search for gifts in November and December, your site should be up and running in August or September. Most users don't look beyond the first couple pages of search results, so it is a big advantage to come up first.
Most search engines filter out sites that try that.
The best approach is to use key words frequently in your site, but not in an unnatural way. In general, the more text in your site, the bigger a target you present to search engines. As long as you use the important keywords in your pages, meta tags won't add much. There are two major don'ts. Don't use frames, and don't use software that generates your pages dynamically.