If you are interested in growing at home you can go 3 ways….
1. The Easy Way
Buy a fully colonised fruting bag – this is essentially substrate (a bag of sawdust or straw) which already has mushroom fibres (mycelium) growing in it. Cut the top off the bag when you receive it, put the bag at around 18c-20c, high humidity (quite easy in the UK in autumn/winter) and out of direct sunlight and you will have mushrooms!
If you dont have these conditions naturally at home, you could simply spray with water a few times a day so they remain damp. Spray less once you see baby mushrooms (pins) start to appear.
Fresh air is important for mushrooms so make sure you have good ventillation.
2. The Medium Way
This is a little harder as you need to put the colonised grain into your substrate bags under (ideally) sterile conditions.
Professionals do this in laminar flow ‘hoods’ which filter competing microbes away from where they are working.
However you can do a more simple heath-robinson version by working close to your gas hob (the flames will push all microbes up and out of the way of your work area). Alternatively, you can build a still air box, which is a plastic box with holes large enough to get your hands inside to work in.
3. The Hard (but most rewarding) Way
If you want to it the hard way you will need to buy or build a laminar flow hood. This keeps your work area sterile while you work.
This is the most rewarding and entails cloning your own mushroom stocks, making agar plates and/or high nutrient liquid cultures, maing your own grain spawn and doing everything from the above two.