The theoretical way of calculating any future is to factor in the current price and holding costs, i.e. interest expenses. If not, then there is an arbitrage opportunity. Arbitrage is a risk less profit earned by buying and selling same securities at different prices and exchanges. The other subjective things that enter the pricing mechanism are sentiments and event expectations. There is a very simple registration module on our home page.
Margin money is like a security deposit or insurance against a possible future loss of value.
This is the money deposited with your broker or exchange to mitigate default risk. Suppose you buy 100 shares of Company X at Rs100, you have an exposure of Rs10,000. In the unlikely event of you failing to honor your commitment, your broker would incur a loss of Rs10,000. The per cent margin is decided on the basis of the maximum price change permitted in a given period. If you margin is inadequate to cover the exposure, the exchange can demand additional funds because of adverse price movement.