Spot meditation can be very short or very long, depending upon your mood and inclination. It involves relaxing into a meditative state, concentrating on an object or picture, and mentally exploring that object. A very good and easy meditation involves a single lit candle. Relax in a chair, and stare at the candle, feel the warmth of the flame with your mind, sense its properties, how it moves in the draughts, mentally feel the candle itself, sense its waxy texture and its shape... explore everything about the candle and flame you can think of. Although this may seem at first read to be a taxing exercise, it is actually very relaxing, and you would be surprised how long you can keep this up. Whilst exploring aspects of the candle, you may be put in mind of an event in your past or a person you are fond of, feel free to explore these thoughts, but keep an eye on the candle.
This sort of procedure can be used for any object, the more interesting the object, the more engrossed you can become in mentally exploring it. This same idea can also be extrapolated to pictures and paintings. Imagine yourself for example, sitting on the bench in the painting, look at the people and surroundings around the bench...
There are specific types of drawings and paintings commonly used for this type of meditation, these are called mandalas and come in a variety of forms ranging from a wheel containing all colours of the spectrum, to complex geometric patterns of different colours. Many examples are for sale on the web, and can also be found in many 'new-age' shops.