Which is the safest way to invest money with minimums risk and maximum returns?

ING has the highest paying money market accounts.

there really is no such thing as minimum risk/maximum return though.

The most reliable investment is US bonds. Zero risk, but low returns. Mutual funds are a pretty good investment, but there is some risk. Try to find one that is fairly diversified so that if one sector of the economy tanks, the whole fund won't tank with it.

The currency market. You can trade currencies online right at home and I've seen huge returns. Any sort of trading you do you must research extensively before putting any money into it. The FX market is what it's called and the returns are very much worth looking into it.
I had a buddy that did it and he made big money off of it in a short time. I saw returns of as much as $200 in 1 day, which is nice if your just doing it part-time. The best thing about it is you can set a stop loss setting, which is where if you hit the point where you have, let's say, broke even where you started you can actually have it stop trading for the day. The market is 24/7 so you can trade all the time. You can have it trading while your at work and set the stop loss and it will just keep making you money. You can actually set it to even trade for a certain time of that day while your at work and have that stop loss.
That's the best idea in my opinion. I'd be doing it but no extra money on my side at the moment. I looked into it extensively about a year ago when it was relatively a small idea here in the US but now it's blowing up pretty big. You can make a lot of money and with the stop loss it's pretty minimal risk.

I hope you make good money and I wish you good luck on any investment you partake in.

the safest way to invest ur money is to gamble it in casinos that way u'll know where u left ur money

Invest into art which is the safest way but beware of scams though returns are maximum but its long term deal u have to have real patiance
my another sugession will be go for property a land or appartment which is the best look for buying some under developing area in the city

U.S. Treasuries are the safest investments you can make. They offer zero risk to your principal and have a relatively predictable rate-of-return. There are a variety of Treasuries to choose from depending upon the degree of risk and liquidity you desire. To avoid the transaction costs of buying bonds, you can purchase Treasuries directly from the U.S. Treasury Department at treasurydirect.gov. If you are interested in investing in equity, buy an S&P index fund. It has minimal transaction costs, is well diversifed, and outperforms the majority of mutual funds.