Application of logic in the potting shed

A logical guide to terms and conditions when gardening under glass:

Perlite =  drainage aid. Mix half and half with potting compost.
Vermiculite = water absorber. Belongs on the surface, not in the midst. If sowing fine seed, add a solid layer of vermiculite over the mixed compost and sprinkle seed over it. The seed will fall down the cracks and germinate (if it feels like it). Sow bigger seed before adding a layer of vermiculite to the surface.

Seeds which will only germinate in the dark = don't worry about that.
Cold stratification = seed which needs a cold spell before germinating. Add seed to damp vermiculite and keep in a jar in the fridge for a few months. Just leaving it in its packet in the fridge = fail.