The following text is from Thomas Metzinger’s 2009 book ‘The Ego Tunnel – The Science of the Mind and the Myth of the Self’.

Maybe you’ve had a lucid dream yourself; the phenomenon is not rare. If not, you can try a number of different induction techniques. For instance, you can adopt the habit of performing “reality checks” several times a day. Each reality check should last at least a minute. It consists in carefully inspecting your current inner and outer environment for any indications that this might not be ordinary waking reality. Here is a checklist that readers interested in exploring the dream tunnel can use as a guideline.

• Is all the furniture arranged the way it normally is?
• Are the paving stones, the tiles, or the design of the carpet on the floor arranged in the same pattern as usual?
• Do objects or persons suddenly appear and disappear, or do they change their identity?
• Do you know who you are and where you are?
• Do you remember what day of the week it is and when you last work up?
• Are there any gaps in your short-term memory of recent events?
• Does your visual attention shift the way it usually does?
• Are you engaging in any unusual physical activities, like flying?
• Are you constantly trying to remember something you know is of great importance but can’t remember what it is?
• Does your current situation have a metaphoric or symbolic character, or do you have the feeling of being close to an important discovery?

If you perform reality checks of this type several times a day, you have a good chance or eventually becoming a lucid dreamer. By pure habit, you will one day perform a reality check in a dream – and if you are lucky, you will correctly realise you are dreaming.