Batteries always have a marking as to positive and negative.
If you don't see it on the plastic part of the battery near the battery post, then look on the side of the battery near the post. Sometimes it's hidden by the cable.
One good indicator, usually it's the positive post that has a cover on it. Hope this helps.
〉 Answered on Jun 19th, 2008 by Lori Johnson, Owner and Instructor at Ladies Start Your Engines