What to Offer on Sales

We have clients that have never had a sale or don't know how to market their sale to gain a profitable profit. You don't have to have a huge sale. (5%-20% off is great) What items should you have for your sale? (Now this can go a few ways, if you're someone who has a overstock of merchandise, or you just need to make room for more inventory, those items would be good for a sale.) If you offer services such as cleaning, detailing, catering etc. You would want to go with BOGO, adding a special service, or adding extra entrées...All sales do not have to happen the day of. (Meaning you can offer the sale, take prepaid orders, honor the sale to all inquiries, take rein-checks, offer coupons.) How should you market it? A lot of people do this a lot. (Don't wait til the week of or day before, to start campaigning it. Your sales will be slim to none. Always start sales two weeks at least in advance.)