Hi all!
Now I am in the process of designing my first theme and I want to have some videotutorials just like on this site. I would like the post about the video to be just like an excerpt with a miniature image, and when you click on the post you get to the full post with the video and more information.

I have managed to show just the excerpt (just text) to specific categories on the first page, but when clicking on it it shows the post with only the excerpt.

I´m guessing this is a simple design flaw of mine. Should there be a template for single post showing the full post?

And how can I insert an image in the excerpt with a link to the full post? (When I just inserted an image with html it broke my post design.)

I just solved the first issue. A single.php template was just missing.
Now, to insert an image in the excerpt that does not mess up my design and provides it with a link is next on the list.