Search for a Realtor that is willing to forgo his commission on the sale of your house if you purchase another house through him. This is not so easy. Many Realtors cling to their commissions. If you can't find a local Realtor willing to take this type of arrangement, head online. There you will find many options.
Read the fine print of any agreement to be sure you fully understand the terms. You don't want to surprised by an extra fee. Also, be sure that you will qualify for the deal as the Realtor proposes it.
Sign the contract and put your home up for sale. Depending on whether you choose to sell the house yourself or go with a full-service Realtor, you could have either a lot or very little work ahead of you.