oh dear - I lost my full reply
- take two:
First, orchids need to be in the proper stage of growth to spike (can vary), many are seasonal bloomers. So patience is often required.
Den spectabile needs to be quite big before it can bloom - how large is yours? Spring bloomer, I believe (I have one, but not yet bloom size). Fertilizer should be withheld starting in early autumn until there is a spike, or new growth, I believe. Moderately bright light, lightly moist media.
Most Oncidiums require no special treatment to induce spikes - year round moderate to moderately bright light, water before media is completely dry. Some spike on fully matured pbulbs, others on not yet fully matured pbulbs. Blooms from new growth only.
Laelias and Cattleyas may be seasonal bloomers, but some hybrids especially can bloom multiple times a year. Generally require moderately bright to bright light, allow media to dry completely in-between waterings. Blooms on new growth only.