When I was but a young boy and a much less mature and well read person, I would barter with God. We all have probably done this at one time or another. If you give me a new car, then I’ll pray everyday. I would also try to get instant confirmation of what God wanted me to do (see also Mark 8:12). I might say if you want me to do option A then make that man in front of me trip and fall. Or if I was really lazy then option A was heads while option B was tails. In reading the OT, it turns out that I may have not been as far off of orthodoxy as I thought. One way Biblical figures determined the will of God is by casting lots.
There is really no concrete explanation of what lots were or how one would cast them. From the context it would seem that it is likened to the modern day use of dice or flipping a coin. The biggest use of casting lots is in the division of the land amongst the tribes and clans of Israel. The very first time it appears is in Numbers 26:52-56 as a command by God to determine the proper division of the land. Lots were cast and each group received their rightful inheritances according to the result. David also uses lots to determine the roles of temple personnel in 1 Chronicles 24:5 and for the Levitical musicians in 1 Chronicles 25:8.
Casting lots was also commanded by God for the Day of Atonement or Yom Kippur. According to Leviticus 16:7-10, two goats were selected as an offering and after casting lots one would be sacrificed and the other would be set free. An interesting thing about lots is revealed in verse 8. Apparently two separate lots were used, one for each goat. So however they were used, it could not have been a yes or no response like flipping a coin.
Casting lots is used approximately 70 times in the Old Testament and much less frequently in the New Testament. It is possible that the use of casting lots became less popular with its aligning to pagan religion. Cleromancy is a form of divination (attempting to determine the will of God), more commonly associated with pagan religions. Examples of pagan cleromancy might be casting bones or reading cards, where the result is random. 
Lots were used in Acts 1:26 to determine who would be the disciple to replace Judas, but many people think the disciples were in the wrong because Jesus had previously told them in Acts 1:4-5 their next move should just be to await the Holy Spirit.
Although the practice of casting lots or its modern day equivalents are generally shunned ways to determine God’s will these days, it was clearly commanded by God in the Old Testament. It seems that it was used only in very specific instances and never appears to override other forms of God’s revelation, such as the word spoken through His prophets. These are just some thoughts you might want to consider the next time you pull out your Magic 8-ball.
References:
- Everlasting Dominion: A Theology of the Old Testament
- What was the practice of casting lots?
- Cleromancy
- Leviticus 16:7-10
- Numbers 26:52-56
- 1 Chronicles 24:5 ; 1 Chronicles 25:8
- Mark 8:12
- Acts 1:4-5 ; Acts 1:26