Mounting an orchid is a very easy process. What follows is a simple pictorial of the steps.
Why mount your plants? Its a fairly natural way for (most) orchids to grow, and it allows those species that can photosynthesize through their roots to take advantage of that ability. Plus, it looks cool.
First, supplies. You need:
* Epiphytic plant
* Moist long fiber sphagnum
* Cork bark or other suitable substrate
* Cheap acrylic yarn or ordinary twine or fishing line
* Piece of heavy wire, ~4 inches
* Assorted tools
The first step is to water the plant(s), then unpot the and remove all the media. Damp roots are more flexible. Take the opportunity to check the roots and remove any damaged tissue which will be brown and squishy.
In this example I am using a community pot of Phal. braceana seedlings. Most times people mount a single plant per plaque, but what you setup is up to you! Make a test arrangement on the plaque and decide how you want it to look. Keep in mind that the plant will send roots in all directions on the mount, and over time the new leaves will often begin to develop forward and downward for a phalaenopsis, which will change the look a little. Incidentally, this helps water drain away from the crown of the plant which reduces the chance of crown rot diseases.
Place a small pad of sphagnum around or under the roots of the plant and place it back on the mount. The object is not to completely cover the roots, but to provide a reservoir for moisture to help them get established. Depending on your conditions and choice of plants you may even elect to skip the sphagnum and just tie the plant directly to the mount.
Wrap the yarn firmly several times around the root ball and sphagnum to hold it in place. Remember to look out for young roots starting so they don't get broken off. Tie the yarn firmly when done.
Finally, you'll need a hanger. Drill a hole in the top of the plaque. Then bend a small loop in the wire, push it through the plaque and snugly against it.
Bend the other end flush against the back of the mount. Pulling it tight will keep it from flopping around. Bend a hook in the top and thread your tag over it for safe keeping.
Newly mounted plants may require a little more attention until they get established. For a phal, water when the sphagnum dries out, which will be every 1-3 days depending on how much you used and what your temperature/humidity conditions are at home. Over time, the need for water will be reduced, and while the plant will appreciate continued multiple waterings per week it will not be offended if it doesn't get them. In a year or two when the plant starts looking like this one, with roots all over the place, yarn can be removed.