A few key considerations can help you choose the best methods and materials for venting your dryer.
Materials
There are several effective, widely available options for dryer vent. The most common is flexible aluminum ducting, which you can stretch out and bend to follow a desired path. This ducting works well and is very versatile, but it can be a little tricky to expand and place at first. If your vent needs to extend more than 10 feet or so, you may want to look into rigid metal pipe or ducting. This is similar to the heating and cooling ducts in your home and causes minimal air flow resistance, which is important for longer vents. Flexible layered aluminum ducting is also available and may be useful for short distances in an especially tight spot, though it creates more air resistance than regular aluminum. Never use flexible plastic ducting to vent dryers. Although plastic ducts resemble aluminum ones and are fine for venting bathrooms, they don't hold up well to the hot air from a dryer and could catch fire.
Vent Path
Ideally, you want the path between your dryer and the end of the vent to be as short and straight as possible. As vents get longer and include more twists and turns, your dryer has to work harder to push the air, and the potential for lint, moisture and heat buildup grows. Most dryers and vent components include recommended parameters, and the staff at your hardware store can also offer advice. As a rule of thumb, try to keep your vent under 25 feet long and minimize the number of bends (especially 90-degree turns). Where you join ducts or pipes, use metal compression clamps or foil tape to seal all joints and keep air and moisture from escaping. If you run the vent through an unheated attic, insulate that stretch of ducting to prevent condensation from forming inside.
Exit Point
Dryers should always vent outdoors if possible. Locate your vent opening in an unobtrusive spot that is clear of obstructions for several feet and open to good air flow. You may also want to avoid high-traffic or high-visibility areas and places vulnerable to water damage (e.g., the underside of a deck or stairs) to prevent problems with moisture and lint buildup. Venting into a yard or through a roof cap is usually a good choice. In a pinch, you can vent an electric dryer into a garage or, with an indoor venting kit, into a basement, though you will get a lot of moisture and lint in that room. For safety reasons, gas dryers should always be vented outdoors.
Maintenance
Inspect and clean your dryer vent every year to prevent excessive lint buildup and identify potential concerns. Also, be sure to clean your dryer's lint trap with every load, and if possible, avoid using fabric softener sheets, which can add to the lint problem.