Many people, although not denying in their hearts that there is God, find it difficult to believe in God.
First, God is invisible, so if you insist that you have to see in order to believe, this is not the way. In the meanwhile, many believers do "see" God, because their spiritual eyes have been opened.
Second, there is the question of which god to believe. So many religions appear so similar to each other. For example, they all encourage people to do good. Which one should I choose? Basically, there are two kinds of religions: bottom-up, humans pursue God by creating their own religions and gods; top-down, God reveals himself to us. The former is represented by Hinduism and Buddhism, the later is represented by Judaism, Christianity, and Islam. However, to know which one is the true religion, it takes three tests: historical correspondence, logical coherence, and empirical relevance. Historical correspondence requires the events recorded in the religion correspond truthfully to historical events. Logical coherence requires that doctrines in the religion is consistent in logic and not contradicting each other within themselves. Empirical relevance requires that the doctrines are applicable in reality, not causing gridlock in practice.
Only the Judaism-Christianity can pass all the three tests. Of course, you can do your study and find out the result yourself. A few scholars have done a great job, including Ravi Zacharias, and David Wood. A search in Youtube will result many of their excellent talks. For example, for Christianity, no contradiction has been found between the events recorded in the bible and the events recorded in history books. The bible says in the first page about how God created everything from nothing, including time and space. In science, the recent bang theory states the universe has a start, confirming what has been revealed by God himself long time ago in the bible.
Finally, there is a challenge in terms of how to talk with God. You might say, if God can speak to me now, then I will believe in him. Interestingly, God used to talk to a person like that way, which is well recorded in the old testament in the bible. Today, God is still doing that, but only to a small group of people, and mostly, to believers. So for most people, the dilemma becomes: if I can talk with God, I will believe; but you were told, can talk with God if you believe". You are stuck. Who should do the next move, you, or God? But you need a redemption, not God ifyou believe". You are stuck. Who should do the next move, you, or God? But you need a redemption, not God. And and after all, who are we to demand God to talk to yoyo now?
Chances are God will talk to you first because without God's grace, nobody will seek God. He might talk to you in voices, or talk to you by people around you, by things happening to you, and by some inexplicable coincidences in your life. If you respond, God's voice will become more and more clear. We are all at his mercy. We need to understand the status quo between us and God: sin has separated us, to overcome that barrier, one needs to admit that God is the author of our lives, believes that Jesus is the son of God and only he can redeem our sin, and finally confess our sin to him and ask him for forgiveness. Then, the communication channel will be opened between you and God, and you can talk with him in prayer. The more prayer you pray to him, the more you will feel his presence and understand how God responds to you in a personal way that only you can recognize. It could be a life scenario, a voice, could be a vision, a dream, a number, or a prophesy.
Therefore, it is actually not too difficult to believe in God, here is the ABC: admit God is the creator of the universe and our lives, believe in Jesus, and confess our sin to Jesus as your lord. It is not about how you feel and think today, it is a matter of using the free will that God gives to you, to believe in him, to come back to him. (12:17)