To make sure that the broker is not a bucket shop or other type of 'fly-by-night' operation you should check to see if the broker is registered with any offical associations in the country where it operates.
For brokers based in the United States you should check out the NFA and CFTC websites. If the broker purports to be a member of the
National Futures Association (NFA) you can double check this by doing a search for them on the National Futures Association's
Background Affiliation Status Information Center (BASIC) search page.
Another interesting check that can be done is to see how much capital your broker currently has. If the broker is registered as a Futures Commission Merchants (FCM) you can perform a check on the
Commodity Futures Trading Commision's website for the broker's
financial data. Just download the most recent .pdf or Excel file to see how much capital the broker has reported to the CFTC. Make sure to check out the Adjusted Net Capital, Net Capital Requirement and especially Excess Net Capital figures.