[How To] Image on a separated line

Hallo. I was just wodering how to put the image in a post on a separate line from the text.
By Default the image is appearing inline with text which is not nice when you have a wide image that takes about 90% of the space.
right now I am putting 30 <p> or so to movethe text down.
Is there any plugin for it?
May be I am doing something wrong.

Thanks for help!