Credit Cards and Balance Transfers

I've very recently acquired interest in this credit/finance line. Thanks mostly to two of my close friends, one being Golbguru and the other a colleague of mine.

Today for the first time i received a cheque(check) of the money that doesn't belong to me and i hv to pay it back in interest free monthly installments. It may sound weird to few but this is how the 'credit' thing works in US.
The cheque amt is meager $350, which by no parlance is something to brag about, but a start nevertheless.

I am strictly a novice in this, but let me tell you how it works.

0% APR on balance transfers - This is something you will never find in India. Normally the interest rates are 2-3% per month = 24-36% per annum (Annual Percentage Rate). In US you might get a credit card with absolutely NO interest on the money you transfer from you existing credit accounts. What a way to pull your competitors' customers.
But as the credit companies are no fools to loan you interest free money, they wud do a 'hard' credit-check on you before approving you a credit card (which happens for all credit cards that you apply for).
If you qualify you transfer your outstandings from other cred cards to this and enjoy interest-free minimum payments per month. Normally the offer would expire after 6-12-15 months and this is the time when you look for another such offer, from their competitors.
(caution : There might be a transaction charge for balance transfers, in that case, you just ignore that offer. Stay put and wait for next offer).

So now in all this, how can you make money ?
Simple - Transfer your non-existing outstandings from an earlier credit card to this card.
eg. You hold card A already without any outstanding amt and card B is the new card with 0% offer. Lets say your credit limit on card A = $5000 and on Card B you qualify for $3000 balance transfer credit.
So now transfer $3000 to your new card B from card A. The credit card company B will send a cheque of $3000 to credit card company A. Soon your acct A will show a 'credit' of $3000.
Then you call up company A and ask them to send a cheque of $3000 as on their records, you've paid excess money to this card. They would happily issue a cheque free of cost and you get the $3000 - cash (in 2-5 days) which you never owned.
Keep paying the minimum amt due every month on card B with 0% interest. This is a MUST else you lose your 0% interest luxury.

Invest $3000 into whatever options (FD/CD/stocks etc) you feel suitable, and enjoy the returns.

P.S. The colleague & friend i mentioned earlier enjoys about $20,000 credit in revolving balance at 0% APR. At 5% APY (annual percentage yield), he can make about $1000 in a year if he invests the money in fixed deposits.