I would like create a plug in that adds a panel of options to edit post page like the one added by All in One Seo but i cant find any good tutorial of any information about what is the correct action of filter tu use.
Could you point me in the right direction? snippet?
What you’re looking for is a meta box. There’s a decent example on the Codex page, or try looking up tutorials. Here’s a very good one:
http://wptheming.com/2010/08/custom-metabox-for-post-type/
yup- you are talking metaboxes. i always use:
http://www.farinspace.com/wpalchemy-metabox/
b/c it is crazy powerful and has some very, very neat functionality… but depending on what you need it might also be overkill.