Put yourself in position to viscerally feel problems that matter to other ppl
e.g. most college students focus on their own problems: The Pizza Problem. The Tinder Problem. The Friday Night Problem.
Go work at, say, Chevron & get exposed to new problems.
Interesting paradox where in order to develop world-class expertise you may have to spend 20 yrs at NetSuite, but spending 20 yrs at Netsuite could also make you unlikely to be a great founder or found a company in the first place.
If you put yourself in a position where you have actual problems—if you go work at a company, if you start a family, travel, etc—you'll be in a position to have startup ideas.