(I want to say first of all that my heart goes out to all the people and their families who have been affected by the Japan earthquake and it's aftermath. I am praying for them and for those Christians who have been affected as well.)
It is impossible to really recognize a false prophet and/or false prophecies without understanding what the TRUE prophets and TRUE prophecies are. The subject of prophecy is so huge, that I cannot possibly cover everything. One thing to recognize is the difference between what prophets and prophecy was in the Old Testament vs what it is today, under the New Covenant.
In the Old Testament, prophets were required to speak for God, because Jesus Christ had not yet come. "Holy men of God spake, as they were moved by the Holy Spirit." The average believer could not hear from God for himself, like we can today through Jesus Christ. Even King David had Nathan and Gad and other prophets in order to inquire of the Lord, to determine His Will. Job lamented that, "Neither is there any daysman betwixt us, that might lay his hand upon us both." Job 9:33. The daysman was referring to Jesus Christ who would be our advocate with the Father.
Now, by what Jesus Christ accomplished, the veil seperating us from God has been torn. In the Old Testament, they were servants, but we are sons and the Lord desires to have a relationship with us AS a son, in the same way that He had a relationship with Jesus Christ. We are now fellow-heirs and sons (and daughters). Therefore if you are truly a born again son of God, your Heavenly Father will tell you Himself what His Will is for your life. In fact God specifically tells you to ask Him for wisdom and what to do in your life. "If any of you lack wisdom, let him ask of God, that giveth to all men liberally, and upbraideth not; and it shall be given him." James 1:5.
If you are having trouble hearing from the Lord for yourself SEEK HIM and you WILL find Him - it is a promise. I wrote a series on that last year:
Listening to the Lord - Part 1 - The still small voice
Listening to the Lord - Part 2 - The sound of silence
Listening to the Lord - Part 3 - Don't listen to the Old Man
Listening to the Lord - Part 4 - Counterfeits and Spiritual Warfare
Listening to the Lord - Part 5 - Fasting
Listening to the Lord - Part 6 - Conclusion
For good measure I'll throw in: Take Heed that No Man Deceive You
But don't take my word for it. Look in God's word, and search for these things on your own, whether they are true or not.
Here is a good book from Zac Poonen you can read online that can help:
Finding God's Will
Of course, the question arises; How about Agabus? How about Philip's daughters? Well, there is still a need for the office of a prophet. If you look in the Book of Acts - before Agabus came, before Philip's daughters prophecied, Paul said he was "Bound in the spirit" to go to Jerusalem. God had already told Paul HIMSELF not to go to Jerusalem. But Paul was "bound in the spirit" to go anyway. Have you been bound in the spirit? I have - I have fought against the clear instructions of the Lord to me about areas of my life - but I have pushed through (been bound in the spirit) AND suffered the consequences of it. So because Paul was determined, the Lord had to send a prophet to tell him that he would be bound if he went to Jerusalem and we don't know what Phillips daughters prophesied, but it then says, "And when he (paul) would not be persuaded, we ceased, saying, The will of the Lord be done." Acts 21:14. Remember that commas were added by translaters and were not in the original text. But then again - maybe that is just a heresie like my friend Richard was saying. Be a Berean and read Acts carefully and ask the Lord about it for yourself.
Was the Lord able to use Paul after that? Yes. If we tell one of our children to not get into a car and drive drunk and they do it, do they cease being our child. No. If they get arrested and end up in jail, do they cease being our child. No. Would we visit them and make the best of it? Maybe. Could they repent and witness to someone in jail with them and that person gets saved. Sure. Was it then the Lord's Will that they got arrested? No, but the Lord was able to make the best of the situation, and He also in His foreknowledge knew what was going to ultimately happen.
In your life - don't just believe someone who comes up to you and tells you that they know the Will of the Lord for your life or that calamity is going to hit and what that person says, is not something the Lord Himself told you about or to do. No matter how "holy" that person might seem. These "prophecies" you read online? Ask the Lord to confirm them to you Himself before you start forwarding emails to everyone in your address book.
Dear Heavenly Father. You are so mighty and wonderful. Thank you for teaching us what Your Will is individually for our lives and thank you for opening our eyes to the false prophets in our day and time. Praise Your Holy NAME. In the name of Jesus Christ. Amen.