Head over here to activate a free 60 day membership to BJ's. Offer good through 7/5/11. If you've had a trial membership recently you might want to, if you can, put it in a different spouses name as BJ's is getting stricter with the number of trial memberships they allow.
BJ's allows manufacturer coupons to be stacked with BJ's store coupons for the same product and you should be able to use more then one coupon on items that are packaged together. For example, you can use 3 toothpaste coupons on all three toothpastes that are sold as a pack. Some stores may differ on this, so I would call your store to confirm their policy.