Orchid seeds are very tiny - like dust in many cases. Because of their size, they don't have enough stored energy to germinate and grow by themselves. They require a host to provide this energy - in the wild this is a fungus in the soil. Commercial growers use a growing medium with either one of these fungi or nutrients and germinate/grow the orchids under laboratory conditions. These facilities aren't usually available to most people, so they will need to experiment with their orchid seed.  In fact, County Councils have had success by just including orchid seed in their meadow mixes when sowing roundabouts and verges. Some species will associate with lots of fungi (eg Dactylhoriza) and can therefore show leaves within 2 years or so.  Others, have very specific fungal partners and may take a minimum of 5 years to show signs of growth.  Some species require a period of cold to germinate and so are best sown in the autumn or placed in a fridge for 2 to 3 months.

Some Tips for Sowing:
Open packet where you intend to sow, so no seed is accidentally lost.

Use damp finger to smear seed onto soil surface.

Sow near existing orchids as there is a stronger likelihood of the correct beneficial fungus being present in the soil there as well as being the right habitat and soil conditions for success.

 If you are particularly interested in native orchids, it is worth looking at the Hardy Orchid Society website which is packed with information - consider joining!