B1G1 or BOGO means buy one get one free. These sales in and of themselves, might not be great deals. This is a merchandise clearing strategy used by stores to move stuff fast. If the items were marked as 1/2 price, people would probably only take one, but since it is buy one get one free (even though it is really like 1/2 price) people will take two, thus reducing the inventory. Be careful though because sometimes the price is hiked up before the sale, so it is not that great of deal.
BUT, you use coupons now...so buy one get one sales mean a whole different thing for you! You have two great options to make these work for you. First, think of it like you are buying two products, (ie..two at 1/2 price) because you are buying two products. So you can use two coupons. For example, an item is marked B1G1, priced at $2.99, but you have two manufacturers coupons for $1, so you get to use two coupons and get both items for $.99.
Another way to score on B1G1 coupons is to use a B1G1 coupon when an item is on sale at B1G1, so then you end up with two free items! Most stores will do these deals for you, but if you have any questions, just as their customer service desk. Don't try and be sneaky or work the system, but these coupons can be real money savers. Now you know another store secret:B1G1 (or two) free!