Another thread asked what made you first have doubts. For some, I guess there was one particular instance that made them start questioning, i.e. generation change in 1995, UN scandal, child abuse being brought out into the open, but for me it was little things. Here is a partial list.
1) Being in several different congregations and all elder bodies having the same harsh, unloving, judgemental attitude which rubbed off onto most of the publishers.
2) The constant references the society made to themselves about events in the bible that they applied solely to them, specifically the imprisonment of the 8 or 9 men in 1918 and how that was somehow fulfilling bible prophecy, the locusts of revelation being the stinging message they were putting forth to the world, nonsensical stuff like that
3) How submitting to the WTS was like submitting to the scribes and pharisees and Jesus condemned the scribes and pharisees for their hypocrisy, their burdening of the people with all of their rules. This was the big eye-opener for me studying the Greatest Man book and realizing that JW's were no different from the Jews of Jesus day
4) For my husband, it was sitting before a JC with my oldest, unbaptized son who wanted to clear his conscience for having sex with his former girlfriend. No one would have ever known about it, they had broken up and moved on, but my son felt like he should let the brothers know. Instead of commending my son for coming forward, the JC chewed both my son and my husband new hind-ends. It didn't end with the JC meeting, it continued after that if either one missed a meeting, the one brother would chase them down in the parking lot and yell at them even more, my son for giving in to fleshly desires and my husband for not being a better family head. My son wants nothing to do with the witnesses.
5) and finally, I guess it would have to be the so-called "holy spirit appointments" of elders. It was spirit appointed alright, but definitely not holy-spirit.