When Jesus returns, you'll know it. Everyone will. There simply won't be any question about whether or not it has happened.
Thus if anyone tells you He has returned, that person is not telling the truth. It's that simple. No one will need to tell anyone else, because literally everyone will know.
We who believe, because we shall in some sense be caught up in the air to meet Him as He is coming down; because the dead shall literally be raised from the grave, and everyone will stand before Jesus Christ in Judgment.
Since you are not, right now, standing before the glorious Throne of Jesus Christ and transfigured by His grace and power--then no, He hasn't returned.
And as to how you ready yourself for His return? Jesus tells us that since we do not, and cannot, know when He will return we are simply to be faithful to Him as our Lord and Master. So here is how you be ready: Trust in Jesus, and love your neighbor. Live your life as a follower of Jesus. When you sin, confess and repent, knowing God is faithful and just to forgive you. When you have an opportunity to be kind to someone, be kind.
There is an apocryphal story about Martin Luther, where he was once asked what he would do if he were to know for certain that Christ would return tomorrow, his response was "I would plant a tree". While the story is apocryphal, it communicates an important bit of wisdom: The Christian should live every day in a responsible way. Why plant a tree? Because I want to see future generations enjoy the fruits of that tree. So do not put off for tomorrow what you can do today: If you see a person that is hungry, feed them. Someone in need of water? Give them drink. They are naked and in need of clothes? Clothe them. Do unto others as you would have them do unto you, do not worry about tomorrow for today has enough problems of its own. Live every day as Christ's disciple, take up your cross every day, pray hard, confess your sins, believe the Good News, remember your baptism, celebrate the Lord's Supper where you declare the Lord's death until He comes, love others. Be faithful.
-CryptoLutheran