To insert YouTube videos in your Wordpress blog do the following:

1. Login to WordPress admin
2. Go to Options >> Writing
3. Uncheck both Users should use the visual rich editor by default & WordPress should correct invalidly nested XHTML automatically
4. Go to Write >> Write Post
5. Paste the ‘embeddable player’ code for your YouTube video in the write box
6. Publish video

7.For some people before you get to step four, go Under Options hit the Users then uncheck Use the visual rich editor when writing.