First, have your home appraised. A home appraiser can cost a few hundred dollars, but will be well worth the cost. If the housing market is good, you can often set a sale price at 10 percent to 15 percent above the appraisal rate. If the housing market is not so good, then your sale price might be just around the appraised value.
Also have your home inspected before a potential buyer does. An interested buyer will definitely have the home inspected, so you'll retain more control over the process if you've already had that done. You'll know if there are simple issues that perhaps you might decide are worth it to fix -- or not (and let the price reflect your choice). Once you have the list of issues found during your inspection, consult with your state's disclosure laws. There are some issues that must be disclosed, either orally or in writing, such as the presence of hazardous materials. These disclosure laws vary from state to state. However, if the proper disclosures aren't made, you may find yourself on the wrong side of a lawsuit.
Finally, try to put your house on the market well before you're planning to buy your next house. Paying two mortgages at once is a hardship for just about anyone, so try to avoid finding yourself in that situation. Also, be patient and realistic. If you're in a rush to sell, you'll likely undervalue your home. If you aren't realistic about the selling price in the current market, you could overvalue your home and not see it sell at all.