Myth 1: You should submit your URLs to search engines.
Myth 2: You need a Google Sitemap.
Myth 3: You need to update your site frequently
Myth 4: PPC ads will help/hurt rankings.
Myth 5: Your site will be banned if you ignore Google’s guidelines.
Myth 6: Your site will be banned if you buy links.
Myth 7: H1 (or any header tags) must be used for high rankings.
Myth 8: Words in your meta keyword tag have to be used on the page.
Myth 9: SEO copy must be 250 words in length.
Myth 10: You need to optimize for the long tail.

what can you say about this any opinion?

1 => Search engines automatically find you when other sites link to you.
2 => Search engines are pretty smart about figuring out your navigation and site structure. However, creating an XML sitemap certainly can't hurt, and is a good idea if you've found the search engines aren't indexing your most important pages.
3 => When you update your site frequently, the search engines come back more frequently so that they can always have the latest content indexed. However, it doesn't affect where you rank in the results AFAIK.
4 => PPC ads have nothing at all to do with organic ranking.
5 => It's possible to get banned from Google if you link to many "bad neighborhoods", use advanced cloaking techniques to specifically outwit the search engines, etc. If you have a Webmaster Tools account, you can sign in and send an email to Google and they'll usually look into the situation fairly quickly and get you reindexed.
6 => The common theory is that buying links can't hurt you, but if Google finds out that they're paid, they won't help you either. Technically, that could negatively impact you because you'd be throwing away lots of money that doesn't help you. That being said, your rankings can be affected if it's you who is caught selling links.
7 => On-page SEO can be just as important as off-page SEO. Ensure you have clean html code, are making good use of CSS, headings are in H1/H2 tags, quotes are in the blockquote tag, emphasized words use the strong tag, etc. Doing everything the right way will make your site much more spiderable and you'll get more love from the search engines.
8 => It's a good practice of on-page SEO for every page to have a unique page title, unique meta keywords, and unique meta description. When logging into Google's Webmaster Tools, they actually point out when multiple pages of your site have the same page title, so that is proof that Google frowns upon that.
9 => I'm not sure what you mean by SEO copy. However, don't keyword stuff your body content. Write naturally, for a human being, and you'll end up with content that humans like AND search engines like. Search engines don't like when you write just for them.
10 => As a forum owner, where thousands of new pages are created daily all from user-generated content, I'm a fan of long tail keywords ... Ranking for a huge number of different things, each which doesn't drive any significant amount of traffic, but overall, it certainly adds up. It's my way of not putting all my eggs in one basket. Plus, I can just let all the content come naturally and don't have to focus on keyword stuffing my pages to rank for a small handful of super popular keywords ... which will kill my business if I fall off page one of the serps for just one keyword.

No need to submit your site to search engines as it find your site even if you didn't submit it.

Myth 3: Frequent updates to your pages may increase the search engine crawl rate, but it won’t may not increase your rankings.

Yeap, that's what I said

ok i got everything except this point. can u please explain that to me buddy
Myth 9: SEO copy must be 250 words in length.

well i have only heard about this seo myth thing thats why i posted it here. i think the myth 9 is the word content of every page of the site

Its all a myth because google can change the criteria for good SEO anytime they like.