Locate local mattress and furniture stores in your area; find one with a good selection of in stock mattresses.
Discuss your needs with a salesperson, including the size and firmness you're interested in. Lie down on several floor models and test them out. You should spend at least 10 minutes on each bed to get a feel for the mattress. Make your choice.
Ask the salesperson how long that particular model has been on the sales floor, and when they will be bringing in more inventory. This is a prime time to take a floor sample off of the store's hands.
Negotiate a price. If you are shopping in May when stores are expecting new inventory, you can purchase the previous year's floor model for 30 percent to 50 percent off. Offer to pick up the mattress as part of the deal. Most stores are more likely to sell you a floor model at a good price if they don't have to deliver it.