1. They read consistently.
The rich would rather be educated than entertained.
Corley wrote that 88% of rich people "devote thirty minutes or more each day to self-education or self-improvement reading" and that "most did not read for entertainment."
"The rich read to acquire or maintain knowledge," he said.
Corley found that they tended to read three types of books: biographies of successful people, self-help or personal development books, and history books.
2. They exercise.
"Seventy-six percent of the rich aerobically exercise 30 minutes or more every day," Corley said. Aerobic exercise includes anything cardio-focused, such as running, jogging, walking, or biking.
"Cardio is not only good for the body, but it's good for the brain," he wrote. "It grows the neurons (brain cells) in the brain."
He added: "Exercise also increases the production of glucose. Glucose is brain fuel. The more fuel you feed your brain, the more it grows and the smarter you become."
3. They hang out with other successful people.
"You are only as successful as those you frequently associate with," Corley wrote. "The rich are always on the lookout for individuals who are goal-oriented, optimistic, enthusiastic, and who have an overall positive mental outlook."
It's equally important to avoid negative people and influences, Corley said, emphasizing that "negative, destructive criticism will derail you from pursing success."
4. They volunteer.
To surround themselves with good people, many self-made millionaires turn to charity, Corley said.
"This is why so many wealthy people volunteer for charitable organizations, civic groups, or trade groups. It helps them expand their network of other success-minded people," he wrote.
Of the millionaires he studied, 72% volunteered five hours or more every month.
5. They practice "dream-setting."
"Dream-setting involves scripting your ideal future life," Corley said. "In this process, you define your future life, the future you, by imagining all your dreams coming true; then you put it to paper in five hundred to a thousand words."
In his study, 61% of the self-made millionaires reported practicing this planning strategy.
6. They pursue their own goals.
"Pursuing your own dreams and goals creates the greatest long-term happiness and results in the greatest accumulation of wealth," Corley wrote.
While too many people make the mistake of chasing someone else's dream — such as their parents' — rich people define their own goals and pursue them relentlessly and passionately.
"Passion makes work fun," Corley wrote. "Passion gives you the energy, persistence, and focus needed to overcome failures, mistakes, and rejection."
7. They sleep at least seven hours a night.
"Sleep is critical to success," Corley wrote. In his study, 89% of the self-made millionaires reported sleeping seven or more hours every night.
"Sleep accomplishes so many things behind the scenes," including memory formation, he said.
8. They get up early.
Nearly 50% of the self-made millionaires in Corley's study said they woke up at least three hours before their workday actually began.
It's a strategy to deal with inevitable daily disruptions, such as a meeting that went too long, egregious traffic, or having to pick up your sick kid from school.
"These disruptions have a psychological effect on us. They can drip into our subconscious and eventually form the belief that we have no control over our life," Corley wrote. "Getting up at five in the morning to tackle the top three things you want to accomplish in your day allows you to regain control of your life. It gives you a sense of confidence that you, indeed, direct your life."
9. They have multiple sources of income.
"Self-made millionaires do not rely on one singular source of income," Corley said. "They develop multiple streams."
He said that "three seemed to be the magic number in my study," adding that 65% "had at least three streams of income that they created prior to making their first million dollars."
Examples of these additional streams are real-estate rentals, stock-market investments, and part-ownership in a side business.
10. They find and check in with mentors.
"Finding a mentor puts you on the fast track to wealth accumulation," Corley wrote.
"Success mentors do more than simply influence your life in some positive way," he continued. "They regularly and actively participate in your success by teaching you what to do and what not to do. They share with you valuable life lessons they learned either from their own mentors or from the school of hard knocks."
11. They help others succeed.
"Helping other success-minded people move forward in achieving their goals and dreams helps you succeed," Corley wrote. "No one realizes success without a team of other success-minded people. The best way to create your team is to offer help to other success-minded people first."
You don't want to give help to anyone and everyone, Corley said, but "focus on helping only those who are pursuing success, are optimistic, goal-oriented, positive, and uplifting."
12. They're positive.
"Long-term success is only possible when you have a positive mental outlook," Corley said. "In my research, positivity was a hallmark of all the self-made millionaires."
The problem for most people is that they're unaware of their thoughts, positive or negative, he said.
"If you stop to listen to your thoughts, to be aware of them, you'd find most of them are negative," he wrote. "But you only realize you are having these negative thoughts when you force yourself to be aware of them. Awareness is the key."
13. They don't follow the herd.
"We so desire to blend in, to acclimate to society, to be a part of the herd, that we will do almost anything to avoid standing out in a crowd," Corley wrote. Yet "failure to separate yourself from the herd is why most people never achieve success."
Successful people create their own herd and then pull others into it, Corley said.
"You want to separate yourself from the herd, create your own herd, and then get others to join it," he wrote.
14. They practice good etiquette.
"Self-made millionaires have mastered certain rules of etiquette principles you have to master if you want to be a success," Corley wrote.
These include sending thank-you notes, acknowledging important life events such as a wedding or a birthday, eating politely and using table manners, and dressing properly for various social events.
15. They dedicate 15 to 30 minutes a day to just thinking.
"Thinking is key to their success," Corley said. The rich tend to think in isolation, in the mornings, and for at least 15 minutes every day.
"They spent time every day brainstorming with themselves about numerous things," he said, from careers and finances to health and charity.
They ask questions such as: What can I do to make more money? Does my job make me happy? Am I exercising enough? What other charities can I get involved in?
16. They seek feedback.
"Fear of criticism is the reason we do not seek feedback from others," Corley wrote. "But feedback is essential to learning what is working and what isn't working. Feedback helps you understand if you are on the right track. Feedback criticism, good or bad, is a crucial element for learning and growth."
Additionally, it allows you to change course and experiment with a new career or business. As Corley said, "feedback provides you with the information you will need in order to succeed in any venture."
17. They never give up.
"Self-made millionaires are persistent. They never quit on their dream. They would rather go down with the ship than quit," Corley wrote.
In his study, more than one-fourth of the participants said they failed at least once in their business — and picked themselves right back up.
"If you want to be successful in life, you have to persist in the face of seemingly unending adversity," he said.
Kathleen Elkins contributed reporting to an earlier version of this article.