There is a reward for resteeming, replying and upvoting. It all falls under the banner of curating. No, you can only resteem other's posts. Don't resteem if you have just posted as it places the article you have resteemed on the TOP of your feed. Wait at least 3 or so days and then read interesting posts, upvote and resteem if it adds decent curator rewards.

If you have an old post that you want to get attention , someone can resteem it for you. It is frowned upon to re-submit a post you have done previously and can have you downvoted. Hope that makes sense!