Johanna Draper-Carlson explains how to get yourself added to review comp lists:
You look cheap and greedy if you start asking for review copies before you have a substantial body of reviews to show your ability and dedication. Write well, a lot, and regularly.
When you put up your site, there’s nothing wrong with including a brief notice in the sidebar, something to the effect of “Review copies may be sent to me at (address)” or “Please email me for information on where to submit review copies” (if you don’t want to publish your address; if you do, I suggest using a PO Box). But don’t start asking everyone and their dog for free comics until you’ve been doing this a while and can show consistent publication.
Worth noting is the first of her “other tips” on the subject: “You won’t get on DC or Marvel’s comp list.” No free copies of every issue of Avengers for you, sadly…