in general it is a good idea to have the keyword in the first paragraph, the title, and if possible include links from one post to another in every article, it gives great internal linking juice. Lynn does it on all the posts at clicknewz. If you have a picture be sure to name it with your keyword dirt-bike-grear.jpg or what ever is in the post.
Find a few sites that have keyword luv and include the keyword in the name@keyword part of the comment.