How do you know for sure that God is real?
There are at least three ways we can know God is real.
First we know God is real through the Bible. The first words of the Bible are, ”In the beginning God created the heavens and the earth…” (Genesis 1:1) The Bible is a book all about God–who he is, and what he has done. The Bible is also God’s Word to us (2 Timothy 3:16). Through the Bible God speaks to us. So if we want to know God’s is real, the first and best place to go is the book that is all about him and full of his words.
Second we know God is real through nature. Romans 1:20 tells us that God’s has made himself known in nature “since the creation of the world, in the things that have been made.” We when we study nature we discover that much of creation is full of beauty, order, and design. And that tell us there must have been someone who created, order, and designed in all.  Would you believe someone if they told you that your bike built itself? Of course not, because things as complex as bikes have to be designed and built by someone. It is the same way with nature. Complex things don’t just build themselves. They need a builder (like in Minecraft). So nature points to the great builder God himself.
Finally the third way we can know God is real is through experience. In John 14:21 Jesus says, “Whoever has my commandments and keeps them, he it is who loves me. And he who loves me will be loved by my Father, and I will love him and manifest myself to him.” When we obey and love Jesus, we get to experience the love of God. And Jesus makes himself known to us (that’s what manifest means). I can tell you the longer I have walked with God and done my best to obey and love him, the more I know for sure that he is real. How do I know he is real? We’ll because I am in a relationship with him. So I know he is real like I know my mom or dad is real. I talk to him, he talks to me. I’ve seen him help me. And I’ve felt his love his love for me.
So if you want to know God is real, I encourage you to spend a lot time with God’s Word, then spend a lot of time with God in creation, and finally do your best to obey and love God. There will still be times of doubts (and that’s okay). But the longer you do these three things, the more you’ll know for sure that God is real.
 Norman Geisler and Ron Brooks. When Skeptics Ask: A Handbook on Christian Evidences. Baker Books. 1990. p.16