It's supposed to happen tonight at 6pm. So I thought I better comment beforehand: No, I don't Jesus is returning tonight. I don't think the Rapture is happening tonight.
So why am I giving advice on how to prepare for the end? Because your life or my life may end today, just like many lives ended yesterday and will end tomorrow. So how do we prepare for it? If you're an atheist, you believe that the end of your physical life is the end for you. I disagree, but I won't argue with you. The point is that there is at least the possibility that you are mistaken and that you will continue to exist after your physical body comes to an end. If so, is there something you can do about it today? I could tell you to ask Jesus into your heart. But you don't believe that Jesus, if he existed, was more than a mere human being. So what would be the point? So I won't tell you to do that.
What I will tell you to do is what Jesus told people to do: Be merciful. If someone has wronged you, forgive him. Why? Because if it turns out that there is a God, He will then be merciful to you.
Take care of those around you. If you see people in need, help them. It may only mean a kind smile and an encouraging word. It may mean more: giving money to someone who really needs it. Giving a ride to someone who really needs it. Visiting the sick or those in prison.
Why? Because, if there is a God, then your purpose on Earth wasn't so you could just help yourself. You were put here to love and take care of others.
In other words, the way to prepare for the End of the world is the same way you should prepare for the End of your life. Live as if God exists, even if you think He doesn't. That way, just in case you're wrong, you've got your butt covered.