Search engines keep the game challenging by frequently changing the “rules” by which they play

Fortunately for us there are some constants we could follow:
Exceeding the maximum allowed characters for html tags may result in either rejection for spamming or an engine acknowledging the tags only up to the acceptable character limit meaning they won’t even read the tags that go beyond the limit. General rules of thumb: 60 characters for the title, 150 for the description and 874 for the keywords. When counting the characters you must include spaces and commas.   Excessive repetition of tag words is considered spamming and may result in spamming penalties or engine rejection.   Excessive submission of your Web site to an engine can result in permanent banning from the engine. What is considered “excessive” varies by engine. Some allow only one submission ever (be careful with the dmoz search engine), some one per day; some allow three or more submissions per day – so you can submit site URLs other than the home page.   Many people make the mistake of only submitting the home page URL. This is very important; much of your traffic arrives through “side doors” instead of through the home page.   Keywords should be “grouped” in categories within the Meta tags and on the page text content.