I think what I found attractive about JW's was that they could disprove what other religions believed, and they could prove what they believed, using the Bible. That seemed so powerful to me at the time (I was 16). Trouble is, I never went to those other religions and asked them to explain it. I talked to a few members of those churches, but they weren't well-informed about their faith and didn't have any answers. It seemed that the Witnesses were bang on right.
Only years later did I begin to question those doctrines. Doesn't the Bible warn us not to go beyond what is written? (1 Cor. 4:6) So where does the Bible tell us not to celebrate birthdays? They have a lame excuse for it, but the Bible never tells Christians not to do it. It's a made-up rule, going beyond what is written. (See full write up on birthdays at http://www.thebentinel.com/jw-birthdays.html)
What about blood? The Bible says to "abstain from blood", right? (Acts 15:29) Not exactly. In Acts 15:29, it says to "keep abstaining from things sacrificed to idols and from blood and from things strangled and from fornication." Note that they were being told to 'keep' doing it. It wasn't a new law, or a revision of a law, it was telling them to keep following these laws that they already obeyed. So by saying 'abstain from blood', they were continuing the law given to Noah to not EAT blood. Some carry that 'abstain from blood' phrase to the point where you'd think we weren't even allowed to touch it. But if a strangled animal was on your doorstep, do you think God expects you to leave it there forever, to 'abstain from it'? Hardly. The law was meant to keep Christians from eating unbled meat.
Of course, Witnesses say that a blood transfusion is like eating the blood. After all, it goes into your body either way, and if a doctor told you not to drink alcohol, would it be ok to inject it into your veins? Well, that's an illustration OF their point, it doesn't MAKE their point. For instance, if a doctor told you not to eat liver, would you still be able to get a liver transplant? Blood is an organ (a fact acknowleged by the Watchtower) and a transfusion is a transplant of that organ. Just like the liver, you aren't "eating" blood when you accept a transfusion. There may be medical risks inherent to accepting blood, but they have nothing to do with the religious issue.
There's two central doctrines of their faith that you can easily blow away using the Bible and some reasoning. Why not ask the person conducting your study to explain them? But don't just accept whatever reasoning they give you, really think it through. Does it make sense? Do the scriptures they cite actually support the position they take?
I believe that after you look at them critically for awhile, the fears you have of going against them will lessen.
Take care,
Dave