Now that the bull market is past the middle stage, but not near the end of its cycle, investors need to keep it simple and be stupid, noted investor Ken Fisher told CNBC on Thursday.
That's because in this part of the normal bull market, fewer and fewer stocks lead the market and those that do are bigger and bigger, he said.
"You want to keep it real simple so you don't snatch defeat from the jaws of victory. And the way you do that is to focus on big, simple names," Fisher, founder and CEO of Fisher Investments, said in an interview with "Closing Bell."
That means big names with diversified revenue and fat gross margins, the ones that "the last greater fool that would get into the market just after it peaked" would buy.
Read More Dow 18,000 just the beginning: Pros
"The stock picker always like to dip down for the fancy and the exotic," he said. However, since right now it's all about bigger being better, "You don't want to play that. You don't want to be too cute. You don't want to be too smart. You want to be stupid."
Specifically, he likes health care and tech, and advises that investors diversify among big, easy names.
Read More10 stocks everyone will brag they own
Disclosure: Fisher Investments owns BNP Paribas, Walt Disney, Novartis and Microsoft across various firm portfolios