Whenever I am asked my opinion on this matter, I usually respond by sharing a bit of wisdom I gleaned years ago from Rev. Bob Marcaurelle, who says, "Is it right to 'put out the fleece' and ask God to give a sign to prove His word or provide guidance? (I would answer that) it is permissible under certain extraordinary conditions but not advisable under most. When all resources of thought and prayer are exhausted God may give us a tangible sign; but such cases are rare."
Besides, if we are not careful, we could end up like the man in the old story who liked to just open his Bible and read the first verse that came to him, believing it was sign from God for him to follow. The first verse he happened to turn to was Matthew 27:5 which says Judas "went and hanged himself."
Since he was not sure how this verse applied to him, the man flipped to another passage and the Bible fell open to Luke 10:37: "Then said Jesus unto him, Go, and do thou likewise." At this point, the man was quite upset, and he did not know how he could ever obey that, so he decided to turn to one more place for one more sign.
So, once again he opened the Bible at random; and to his horror, his finger fell upon John 13:27: "Then said Jesus unto him, That thou doest, do quickly."
As Rev. Marcaurelle admonishes: "It is dangerous to make circumstances or miracles the basis of obedience." The man in the story would have been far better off to have read the Bible systematically and applied its teachings to his life holistically, rather than taking small bits of Scripture out of context as if they were miraculous signs of direction from God.
Remember, Jesus Himself said that only an evil and adulterous generation seeks continually to prop up its faith by looking for a sign (Matt. 12:39).