1. Four mutually exclusive things: clear skies, no moon, no school(work) and major shower peaks.
2. Meteor activity will be low until you decide to take a break.
3. Meteor activity will be low until you fall asleep.
4. While watching a major shower you will see only one meteor in several minutes, many will appear while you're recording the lone meteor you saw.
5. If you're facing north, most meteors will appear in the south.
6. When you turn south, most meteors will appear in the north.
7. When you install a fisheye meteors will disappear altogether.
8. When a fireball appears you will invariably be looking 180 degrees in the wrong direction.
9. When a fireball appears you will invariably be looking at the ground.
10. When a fireball appears you will invariably be recording a +5m meteor.
11. When a possible minor shower meteor appears you will remember its path, but you will forget its direction.
12. When a possible minor shower meteor appears a gust of wind will appear out of nowhere and blow your charts downhill.
13. Meteor activity will be nonexistent until you must take a sanitary break.
14. Meteor activity will be low until you become really hungry.
15. The diameter of stars is linearly proportional to your teff.
16. The number of meteors is exponentially proportional to your teff.
17. During an uncharacteristic stretch of clear skies the peak night will be cloudy.
18. Your taperecorder will die during the most active period.
19. Your pencil will die during your most active period.
20. Your torch will die during the most active period.
21. A possible minor shower meteor will invariably appear in Camelopardalis.
22. A fireball will invariably appear in Camelopardalis.
23. A fireball will invariably appear in your camera's field of view in between exposures.
24. A fireball will invariably miss your camera's field of view by a couple degrees.
25. When a fireball appears it will invariably appear in the part of the sky that's not on your charts.
26. When it's clear your LM will be poor.
27. If your LM is great you will either become sleepy or fog will lift.
28. Fog will lift anyway.
29. If the weather is poor and you go chasing clear skies, it will eventually be clear home.
30. The largest telescopes you've ever seen will invariably be present during the peak night.
31. The radiant of a very weak possible new shower will invariably be best placed for observations in early April evenings.
32. Two mutually exclusive things - clear skies and no moon.
33. If it's clear all day, it'll be cloudy that night.
34. You will invariably be grounded due to committments during those LM7 nights.
35. If it's clear and there's no Moon, it will be brutally cold and the wind will be blowing like a hurricane.
36. When you catch a fireball on your camera the photo will be out of focus.
37. Perfect photos will be ruined by the lab.
38. The product of the number of shower meteors and the desire for their processing has a constant value.
39. If you observe 364 nights a year, the outburst will happen in the 365th.
40. If you observe 365 nights a year, there will be no outburst.
41. Your wife/husband/boyfriend/girlfriend's birthday will be on January 3, August 12, November 18 or December 14.
42. If you observe from your backyard your neighbour's dog will have a sleep disorder.
43. If you observe from your backyard your neighbour will have a sleep disorder and spend the night in a brightly lit kitchen, which will invariably be facing your backyard.
44. If it's been clear whole July and up to August 12, the latter date will invariably be cloudy.
45. If it is by some coincidence clear it will be unseasonably cold.
46. If winter has been mild so far there will be a blizzard on December 14 and your favorite observing spot will be burried under a meter of snow.
47. You will catch a cold on December 13.
48. You will get over the cold quickly but you will be ill again on January 3.
49. Your mid-term exam will be on January 4.
50. When you arrive to your favorite spot for the Geminids you will forget: gloves, extra socks, warm drinks.
51. You won't observe the Geminids since it's full Moon.
52. If it's not full Moon you will be under the only cloud within miles.
53. You will always enjoy clear skies when the Moon is full. You won't when it is new Moon.
54. If an outburst is predicted it will occur 16 hours earlier and you will miss it.
55. If you prepare and observe 16 hours earlier there will be no outburst.
56. If its crystal clear there will be a lone patch of cirrus passing during the outburst.
57. It will always be clear during the nights before the maximum from a big meteor shower. The maximum night will be clouded out.
58. There is no such thing as luck.
59. If there is, luck has nothing to do with it.
60. There is always this observer in Florida Keys/Sacramento Mountains/Mauna Kea...
61. Sooner or later there will be a streetlight installed that illuminates your backyard.
62. When you go break it, you will invariably get caught.
63. If you don't get caught you get electrocuted.
64. Your tape will get jammed during highest activity.
65. In March or April your tape will get jammed in early evening and you won't notice it till morning twilight.
66. You're smart and you record your meteors on paper. In morning twilight there will be a gust of wind and it will blow your paper away and you will never see it again.
67. Your alarm clock will fail you.
68. Your backup alarm clock will fail you too.
69. Your backup backup alarm clock will fail you as well.
70. Zzzz...
71. You will unkowingly lie down on a small rock. By morning twilight it will feel like a house sized boulder.
72. There is no such thing as luck.
73. If there is, luck has nothing to do with it.
74. If your neighbours don't have a sleep disorder and don't have a dog, they will invariably have a large tree that will block out a good part of your field of view.
75. No, they will not cut it down.
76. After you've seen a good display there will always be this guy in Florida Keys/Sacramento Mountains/Mauna Kea who will have his LM a full magnitude better and will have seen many more meteors.
77. After you've seen a poor display there will always be this guy in Florida Keys/Sacramento Mountains/Mauna Kea who will have his LM a full magnitude better and will have seen a great display.
78. Leonids don't peak over your longitude.
79. There will always be this guy in your group with 0.5mag better LM.
80. There will always be this guy who logs 300+hrs teff every year.
81. If you leave your meteor observing form on your table your dog will chew it.
82. If you operate 7 cameras and have 95% sky coverage, the fireball will appear in the uncovered 5%.
83. If fog lifts it will invariably be 3m higher than you can possibly get. Above that it will be perfectly clear. Bortle Class 1.
84. The Perseid peak and the only thunderstorm in summer will invariably overlap.
85. If the sky clears after the thunderstorm and in time for the peak, fog will lift.
86. Your photocopier will break down at 1am while reproducing your vital star charts.
87. Your reclining chair will break down on August 12 at 7 pm.
88. There will be a major (historical) auroral storm during the major shower peak. Next night there will be no aurora and no meteors.
89. You began serious meteor astronomy career a couple of days after: Aug 13 1993, Nov 17 1998, Nov 18 1999...
90. Draconid outbursts will ALWAYS occur over Japanese longitudes.
91. Sooner or later you will receive a visit by a friendly hedgehog. Sooner or later you will receive a visit by a not so friendly wild boar.
92. You will get distracted by a small rodent in the same instant a fireball appears.
93. If you brought N pencils you will always need N+1 pencils.
94. There will be a supernova during a Leonid meteor storm.
95. There is no such thing as luck.
96. If there is, luck has nothing to do with it.
97. Meteor predictions will be accurate forever, until you decide to observe.
98. The more inconspicous the stream, the more likely it is to outburst. You will therefore miss most (all) outbursts.
99. If there is an outburst, you will be caught unprepared.
100. Bright fireballs won't happen to you.
101. If your taperecorder and talking watch work well, there will be nothing to record.
102. Most of your 'observing expeditions' will end with an 'I should've stayed home'.
103. The ones you stay home are the most successfull.
104. You will be ridiculed for your fireball observation, since there was obviously an alien invasion.
105. If a storm is predicted, the radiant is in south hemisphere.
106. The radiant is located 1 degree below horizon, at your radio-scattering observing site.
107. There will never be observers at the right place to observe your predicted maximum. So you will never know if your predictions are right or wrong.
108. If theory is right, there is no observer. If theory is wrong, there are lot of observers.
109. Your predicted maximum occurs when the radiant is above the middle of Pacific ocean, Antartica or South Africa.

Quoted from MBK Team at http://www.orion-drustvo.si/MBKTeam/meteors/murphy.htm