[xdude]

Many people in this thread use plugin like yoast or Seo Aio . I'm using this plugin too . But how to seo a wordpress blog manually ?

Then you need to go edit source code of Wordpress to do some changes also add things like Google webmaster code etc into footer or header by editor. There is really no point and real gain in that. Plugins let you do all these stuff easily without messing your code.