Avoid overwatering which leads to the demise of many more orchids than underwatering. Constant wetness will cause the roots to rot, which leaves the plant without a means for taking up nourishment which then causes the leaves to droop and will eventually kill the plant. The classic advice is to water the day before the plant dries out. If you have to let the plant go dry to figure out what a dry plant weighs, it will not kill the plant and will make you a better grower. Another measure is to use the pencil trick (the point of a sharpened pencil, when inserted into the medium, will darken with moisture if the plant has enough water). And, there's always the old standby - put your finger in the mix. If it feels wet, it is wet. If you aren't sure whether it is time to water, wait one more day.

Another type of orchid you can grow at home is what I call the “Thai restaurant orchids.” These types of orchids are Dendrobium hybrids and can be found at Thai restaurants that decorate their tables with freshly-cut flowers. They come in many colors (white, green, purple, pink, yellow and more) and require a fairly warm environment. In fact, they could loose their leaves in the winter when the ambient temperature drops below 60°F (15°C) or so. But the “Thai restaurant orchid” is really just one small group of hybrids within the Dendrobium genus. Dendrobium is actually one of the largest orchid genera.
The Lycaste orchid genus, similarly to its relative Anguloa, likes intermediate-to-bright light, intermediate-to-cool temperatures, and high humidity. The flowers look rather different, though; they are more-or-less triangular in shape because the sepals point outward while the petals point forward. These orchids are very fun to grow, and will thrive if you get their care right.
With a shape that is similar to a dancing lady, the Oncidium orchid is low-maintenance and easy to grow, and it comes in stunning colors such as bright yellow and gold. The variety called Sharry Baby has a chocolate-like scent, and although simple to grow, the Oncidium orchid does require a lot of moisture and humidity to thrive. If you notice any type of deformities in the leaves of this plant, it is likely because this requirement has not been met. They are truly beautiful bloomers.
The den-phal type are warm growing year round and do, just by happenstance, bear flowers similar in appearance to the genus Phalaenopsis. They can be distinguished by plant habit (most Dendrobium have pseudobulbs that resemble tall canes) and flower shape. Den-phals have a spur at the back of the lip; some are more pronounced, others less. They are also borne on very strong upright to barely arching stems. Interesting to note, den-phals can rebloom on old canes.
Dendrobium is a massive genus containing more than (conservatively) 900 species. These range from cool-growing miniatures to huge specimen plants growing in hot conditions year round. The most commonly found types of Dendrobium are the phalaenopsis type (commonly known as den-phals, and named for the species most used in their breeding, which used to be known as Dendrobium phalaenopsis, but which is now known as Dendrobium bigibbum), and the nobile type (named for the species most used in their breeding, which is known as Dendrobium nobile).

The leaves of some orchids are considered ornamental. The leaves of the Macodes sanderiana, a semiterrestrial or rock-hugging ("lithophyte") orchid, show a sparkling silver and gold veining on a light green background. The cordate leaves of Psychopsis limminghei are light brownish-green with maroon-puce markings, created by flower pigments. The attractive mottle of the leaves of lady's slippers from tropical and subtropical Asia (Paphiopedilum), is caused by uneven distribution of chlorophyll. Also, Phalaenopsis schilleriana is a pastel pink orchid with leaves spotted dark green and light green. The jewel orchid (Ludisia discolor) is grown more for its colorful leaves than its white flowers.

Always use a water breaker (a water diffuser that you attach to the front of your hose to soften the flow of water): For only a few orchids, a sprinkling can with a long spout with a rose (a water diffuser placed on the end of the water-can spout) that has many small holes works well. These devices allow thorough watering without washing out the potting material.
Oncidium, perhaps more accurately the oncidium alliance, are a group of plants from South America that span a wide range of habitats. Inside the oncidium alliance there are a number of genera that hybridize freely to create what we call intergeneric oncidium hybrids. These can come in all sorts of shapes and sizes but are generally characterized by large quantities of small to medium flowers borne on a branched stem that generally forms a Christmas-tree shape. The most commonly identified Oncidium are the yellow “dancing lady” type.
Always water early in the day so that your orchids dry out by nighttime. The proper frequency of watering will depend on the climatic conditions where you live. In general, water once a week during the winter and twice a week when the weather turns warm and dry. The size of your orchid container also helps determine how often you need to water, regardless of climate conditions. Typically, a 6-inch pot needs water every 7 days and a 4-inch pot needs water every 5 to 6 days.