There is a lot of information and misinformation out there about SEO (Search Engine Optimization). There are companies and individuals claiming to be experts that give advice and do things for clients that will hurt more than help. And remember: there are also a lot of old websites out there. I’ve seen more new sites than I can count that parrot outdated information.
So rather than work from secondhand information, take it straight from the horse’s mouth.
Read what Google has to say on the subject, directly from Google’s own site. Pay close attention the bottom of the page on what not to do too.
They’ve got lots of other information available too. Remember, not all search engines work the same, but a lot of them have followed Google’s lead. The information Google provides holds true for improving search engine rankings for many search engines.