Inherent Conflict

One way to guarantee conflict in your story is to have protagonists with directly competing goals or outlooks.

An oft-used example is "the fireman and the arsonist". We also see the FBI agent and the hacker, the cop and the vigilante, and so on.

But keep in mind that conflict doesn't equal career. Inherent conflict can come from very basic outlooks on life.

Ex:
Rule follower vs Rule breaker
Globe Trotter vs Homebody
Orderly mind vs the free spirit
Ends Justify Means vs Follow Procedure
Introvert vs Extrovert
Reliability vs Impulsivity