4 self-made millionaires share their No. 1 strategy for building wealth

Courtesy of David Bach. "Many of you are actually going to save a fortune on your tax returns," says David Bach.

The wealthiest people focus on earning .

"While world-class thinkers understand the importance of saving and investing , they direct their mental energy toward accumulating wealth through serving people and solving problems," writes self-made millionaire Steve Siebold in "How Rich People Think," which he wrote after studying millionaires for over 25 years.

Here are four strategies to build wealth from self-made millionaires who have done it.

1. Develop multiple streams of income

"You won't get rich without multiple flows of income," says self-made millionaire Grant Cardone , who was deep in debt before reaching seven figures . "That starts with the income you currently have. Increase that income and start adding multiple flows.

"You want what are called symbiotic flows. Do not just add disconnected flows. Instead, find other ways you can add income to the job you already have. My video guy does advertising for me — and after proving himself, he started making advertisements for those connected to me. He didn't start a doughnut shop."

2. Invest your money — every single day

In just five years, Grant of Millennial Money went from having $2.26 in his bank account to $1 million. On his blog, the 31-year-old self-made millionaire shares " the single most important hack " he's used to build wealth: "I break down ALL of my money goals into daily goals. I still deposit money every day into my investment accounts."

He started with the goal of setting aside $50 a day. At first, "some days it was only $5, but I rarely missed a day," Grant says. "Then I started trying to make as much money as possible every day so I could invest it. I stopped thinking long term and thought every day about making that $50 threshold."

His daily goal of $50 deposits soon became his daily minimum. He started setting aside "$70, then $80, then $100 dollars a day. … Then as my side hustles started really taking off I started depositing $500+ a day. ... Then I put $5,000 in a day, then $20,000, and the rest is history."

3. Pay yourself first

According to self-made millionaire and bestselling author David Bach, there's "one, proven, easy way to get rich," and that is to pay yourself first . What that means is simple, Bach writes in "The Automatic Millionaire": "When you earn a dollar, the first person you pay is you."

Most people don't do this. "What most people do when they earn a dollar is pay everyone else first. They pay the landlord, the credit card company, the telephone company, the government ...," Bach writes. They pay themselves whatever is left over.

The key to paying yourself first is to make it automatic , meaning, to have money taken out of your paycheck and sent straight to your savings, retirement or investment account. After all, "you can't spend what you don't have in your pocket," Bach says.

4. Change your mindset about money

"Getting rich begins with the way you think and what you believe about making money," writes Siebold in "How Rich People Think."

The author continues: "The rich eventually figure out that training your mind to find solutions to difficult problems is the real secret to making money. The good news is this is possible for anyone who conditions their mind to think this way, and then transforms thought into action."

Also From CNBC

Watch The Profit on Yahoo View, available now on iOS and Android.

More From CNBC