One of the most disciplined investors of all time, Warren Buffett and Berkshire Hathaway (NYSE:BRK-B) (NYSE:BRK-A) stick to a specific set of rules with every investment that they make. It is this system that has allowed Buffett to deliver staggering returns over his illustrious career, and it also explains why he won't buy "it" stocks like Apple (NASDAQ:AAPL), Tesla Motors (NASDAQ:TSLA), and (NASDAQ:AMZN). So, why change a working formula? Here are a few of the rules of the Warren Buffett way and eight investments the Oracle of Omaha would never make.

The 100 year rule
This is a phrase Buffett has used in letters to his shareholders to justify certain investments. Basically, he invests in industries that are virtually guaranteed to withstand the test of time. Take a look at Berkshire's current holdings, and you'll see a lot of insurance businesses, food manufacturers, banks, and construction companies, to name a few. People will always need to insure their lives and possessions, safe places to keep their money, homes to live in, and food to eat.

What does the company do?
If he doesn't understand what they do, he doesn't invest in it. When Buffett dismisses a new tech investment, he often gets called "an old guy who just doesn't get new technology." Well, that may be true, so why would he throw billions of dollars into it? Just because other people are?

Competitive advantage
To find out if a stock could be considered by Buffett, once it passes the other two rules listed, it must have an identifiable competitive advantage in its industry. Coca Cola has tremendous brand recognition. Wells Fargo has some of the highest-quality assets of any bank.

This is by no means an exhaustive list, and there are plenty of other things Buffett looks for when investing. However, by using these three simple rules, we can identify tons of very popular companies that Warren Buffett would never have any interest in buying. Here's a slideshow with a few examples...

Follow along as we countdown the days until Berkshire Hathaway's annual shareholder meeting in Omaha, Nebraska on May 3. A handful of Fools will be attending the event and live chatting with other Fools around the globe! Click HERE to set a reminder for yourself about the live chat!

The previous articles in our "12 Days of Berkshire" series:
12 Reasons Warren Buffett Is an Incredible Investor and How You Can Learn From Him

11 Things in Your House Making Warren Buffett Money

10 Reasons Berkshire Hathaway Is the Best Stock You Can Buy

9 Warren Buffett-Approved Dividend Stocks