ANSWER: Parapsychologists have begun to recognize a number of physical and psychological factors that can influence psychic functioning. These include:
Geomagnetic Fields (GMF):
The Earth's geomagnetic field is in a constant state of flux, affected in part by solar activity, a daily GMF cycle, and the lunar cycle. Some studies suggest that ESP improves as GMF fluctuations decrease. In other words, low GMF may be good for ESP. Similarly, ESP hit rates appear to increase both in the lab and in the casino around the time of the full moon. On the other hand, geomagnetic highs have been reported with the onset of some poltergeists. However, this finding has not been a consistent one, and the effect may be complex and interactive with other variables.
Local Sidereal Time (LST):
Local sidereal time is an Astronomy term, referring to how the planet is oriented relative to the position of the stars. Once a year it will match clock time (on the Autumn equinox), otherwise it's different, changing by 6 minutes a day. Fortunately. it is easy to find free software to calculate it out for you on the internet. Why do parapsychologists care about LST? Because if you look at studies done around 18:00-19:00 hours local sidereal time (LST) ESP hit rates drop to zero. However, if you look at around 13:30 hours LST, there is a 400% increase in ESP hit rate. Moreover, this appears to be the most consistent finding across over two decades of research by every experimenter in every laboratory around the world. It is consistent. Some have speculated that the effect has to do with how we are positioned on Earth relative to the galactic core. When most of the Milkyway Galaxy is hidden below the horizon, ESP peaks. On the other hand, when the galactic center is overhead, the ESP hit rates drop to zero.
Some studies suggest there may be an interaction between the phase of the moon (in particular, a full moon) and solar activity which can modulate some types of psi. However, this has not been well studied and it is probably too early to draw much in the way of conclusions.
Other than Telepathine (also known as Ayahuasca), which is used in religious ceremonies in Brazil, there really aren't any drugs which are thought to enhance psi abilities. In the 1960s a great many people used hallucinogens to enter altered states, but most of the investigators who explored these lines found them to be dead ends in the long run, and now recommend using either meditation or holotropic breathing methods (a form of hyperventilation) instead. I have seen a number of cases in which amphetamines, or speed, triggered paranoid hallucinations (both visual and psychic), which could persist for a surprisingly long time after the drug was ingested, sometimes for many months. Those with psychic talent may be quite sensitive to chemical substances, and should be very careful about using them.
A number of factors affect psychic abilities, including mood and emotion, energy level, psychological need, and others. However, one of the biggest is your state of consciousness. People are naturally more psychic when dreaming and on the cusp of sleep (either waking up or falling asleep). Other states, such as hypnotic trance and during meditation also facilitate psi.