Standard dental floss is generally considered the most effective tool for cleaning the tight spaces between the teeth. You can also use dental floss to scrape up and down the sides of each tooth.
A water pick, also known as an oral pulsating irrigator, is a device that aims a stream of water at your teeth. A water pick can help remove food particles from your teeth and might help reduce bleeding and gum disease — but it isn't generally considered a substitute for brushing and flossing. It doesn't generally remove visible film and plaque on your teeth, but can aid in reduction of bacteria even below the gumline.
If plain dental floss gets stuck in your teeth, use the waxed variety. If you have a hard time handling dental floss, try a floss holder. Other options might include special brushes, picks or sticks designed to clean between the teeth.