Place your furniture in a climate-controlled area. Wood and antiques don't hold up well in extreme heat or cold. Extreme temperatures can cause cracks or warping, both of which will ruin your furniture.
Control the moisture and humidity. Excessive moisture can cause splitting and rotting in wood and mold in fabric. If you store your furniture in a space that gets humid, use a dehumidifier.
Cover it up. Lay a sheet or tarp over each piece of furniture in storage. This protects the pieces from dirt and grime and prevents scratches and dents while you're moving things around.
Stay away from the sun. Never store furniture in direct sunlight. Sunlight exposure leads to fading. Keep things away from windows, and cover items that might be in the path of the sun.
Leave at least 2 or 3 inches between your furniture and the walls to allow for air circulation. This will cut back on moisture and keep items fresh.
Set furniture up on wooden or cement blocks if you are storing it in a basement. This will help avoid water damage in the case of a flood.
Check frequently for insect damage. Look for signs of insects chewing on your furniture or for tiny fecal matter around the area. Contact an exterminator immediately if you see signs of insects; they can cause a lot of damage in a short amount of time.