Possible Duplicate:
What are the best ways to increase your site's position in Google?
Order of HTML meta tags

I'm new to websites in general (which is why I'm starting on blogger) and am just curious as to which tags I should be using in my posts?

My posts generally include a title relevant to the keyword of my blog, an image, a video, my content, and a link to my twitter.

I don't really use any tags and someone mentioned that they may help for SEO. So I figured I would ask for some advice from people who know what they are doing.

EDIT

I apologize for not clarifying, I meant tags such as:

Header tag:

<h1>This is my title</h1> 

Image tags with attributes:

<img src="keyword_image.jpg" width="100" height="78" ALT="this_shows_examples"> 

What other tags and attributes are ones I should use for a well put together website and SEO?