this is such a popular question. both Christians and non-Christians ask about it all the time. many will answer with "it's all a part of His plan". i know it's all a part of His plan, but non-Christians don't really want to hear that, i believe it is over said, and not explained enough.
there is a movie series based on the janette oke "love comes softly" book series. while i was watching each movie, there were two things that really caught my attention from two of those movies.
first, was the answer to the question "how is God really there? you can't see him?" from the 7th movie "love takes wing". it was centered around an orphanage, and a doctor who was trying to cure a sickness that was spreading through the town. this doctor used to believe in God, but ever since she'd gone to medical school she was convinced otherwise, and her husband dying did not help her faith. the owner of the orphanage believed in this doctor because she prayed to God every night about this sickness. she explained to the doctor "even though you can't see God, it doesn't mean he's not there. when you went to medical school you learned about germs. even though you can't see them, you know they exist." this is a great example, even though you can't see germs you know they are there because of all the "work" they are doing. with God, you can't see Him, but you can see the work He is doing through others lives, and you can see that He really exists.
the other line was from the first movie, "love comes softly", and it explains the question "why God?" it doesn't really give a specific answer, but it helps a lot. this is based on a lady who had just lost her husband, and was working with another guy (who lost his wife) and started to fall in love with him. she had never believed in God, but she had asked how in the world he could still believe in God. he lost his wife and his barn was almost burnt to the ground, how could he still trust in a God that caused all this? he explained how he prayed everyday and just knew God would take care of them, but it still wasn't really convincing her. if he trusted God, why would God do this to him and his family? he than said "Missie (his daughter) could be walking right next to me and fall down, that doesn't mean I allowed or caused it to happen." God is always walking right next to us, we may fall or get off path at times, but that doesn't mean God allowed for us to do that.
even though bad things happen to everybody. God will always be right there to pick us back up.