I believe it's best to limit the risk of a margin call to a minimum by implementing this into your strategy. For example with proper money management and with a diversified portfolio.

To make sure my strategy is prone to margin calls, I've included this into my code:

Code
if(Equity - MarginVal < 0)
    {
    printf("\n***CRITICAL***");
    printf("\nMargin Call: Margin (%.2f) >= Equity (%.2f)", MarginVal, Equity);
    printf("\nTheoretical Equity should be: 'Balance(%.2f) + WinValTotal(%.2f) - LossValTotal(%.2f)'", Balance, WinValTotal, LossValTotal);
    quit()//(Optional);	
    }