Here are some suggestions for how one could hypothetically investigate whether they are living in a “real” reality versus an imagined or dreamed one after death:

– Analyze your senses – do they operate consistently and predictably according to known laws of physics? In dreams, senses may act in illogical or changing ways.

– Look for discontinuities – dreams often have abrupt scene or perspective changes that would be improbable in waking reality. Look for inconsistent timelines and transitions.

– Examine memories – in dreams memory can be hazy, contradictory or resetting. Check if memories have gaps or contradictions. 

– Assess logic and critical thinking – dreams may not adhere to rational cause and effect. See if claims and conclusions stand up to careful logical scrutiny. 

– Evaluate independence – are there signs other beings have independent existence and free will? Or do they only appear when you are aware of them?

– Consider predictive ability – can you make accurate predictions about the future based on patterns? Dreams may not follow reliable patterns over time.

– Test rules/physics – do basic scientific principles, laws of physics, etc consistently apply? Dream worlds often have different “rules”.

– Look for extra ordinary abilities – things like flight, telekinesis, etc that would not be possible in a normal waking life.

Of course, ultimately there are philosophical limits on being able to prove any reality “real” or not. But rational analysis and evidence gathering could provide clues about whether one is dreaming or awake. Maintaining skepticism and rigorously testing assumptions is key.