Have you noticed how the snake works? We see a pattern here which is so often the way we get tempted.
First, he gets us to doubt God's word, and to focus on the things God prohibits. So instead of seeing the entire garden of luscious fruit around us, we focus on the prohibition, the one tree God has placed off limits. God has spoken clearly to most of the issues we face. If we know God's word at all, the serpent's tactic is to get us to question or doubt it. This is subtle most of the time -- it's not like one day we face a decision and start to say, "The Bible is false!" No, it's more like this: I know God's word says that "in repentance and rest is my salvation," (Isaiah 30) but I feel the pressure of my to-do list, so I focus on the tasks I want to do rather than on the rest God provides. I think, "I'll rest tomorrow. Or maybe the day after. Today I have to get things done." So I doubt that God knows best, because if he saw all the things I'm responsible for, he would have written that verse differently, right? Or maybe I just think to myself (and this is really subtle) "Yes, God's word says I should rest; but it also says I should work hard, and you have to know how to apply the word." So I step back from the word and begin to debate with myself rather than simply accepting it as the authority over my situation. Step one accomplished.
Second, the serpent denies the penalty for sin that is contained in God's word. "You will not surely die," he says, in direct contradiction of what God had said in Genesis 2. So in the above illustration, I start arguing with God's word. "My salvation doesn't depend on whether I rest or not," I tell myself. Salvation is by grace, after all, and saying it's dependent on rest is some wacky kind of works righteousness. So I get to work on my to-do list, having effectively listened to the voice in my head that says something which, while theologically true, directly contradicts God's word. What I don't realize is that my salvation in this sense is not just about my eternal status, whether I will go to heaven or not; it is a question of whether I will begin here and now to experience the "abundant life" (John 10) that Jesus came to give. So my theological correctness keeps me from experiencing my salvation here and now. Step two accomplished.
Third, the serpent casts doubt on God's character. "God knows that when you eat of it, you will be like God, knowing good from evil." In other words, God isn't willing to share his power, his knowledge, his God-ness. He's holding out on you. How many of us somewhere along the way have bought into the idea that God is something less than entirely good? He messes with us, he holds out on answering our prayers, he creates trouble in our lives for his own hidden purposes, he is not really trustworthy, he is not really good. While he doesn't give me more than I can handle (who came up with THAT idea?) he still dumps bad stuff into my life, or at least lets it hit me. We have believed the snake over and over on this one. The issue is not that we believe God allows bad stuff to happen -- it is that deep down we believe that God has something less than our best interests at heart. Step three accomplished.
Now the snake has inserted enough of a wedge into my relationship with God that rather than knowing only God and receiving all things through God, I'm dealing with the questions on my own. And in doing so, I have already walked away from the relationship with God that he desires, and for which I am created. Taking a bite of the forbidden fruit is only the consummation of a shift that began with me "thinking for myself."