In IRV, the best strategy is to vote honestly; rank your favorite first, second-favorite second, and so on. Ranking a second choice can never hurt your first choice, and if your first choice is eliminated your vote still goes to someone you support. 

A concern with the current vote-for-one plurality elections is that they encourage voters to vote strategically. In the United States, most high-profile national elections devolve into a contest between two front-runners while other third party candidates are disparaged as “spoilers” for splitting the vote of one party. Voters must then vote for the “lesser of two evils” or risk “throwing away their vote” to an underdog third party candidate.

IRV largely resolves this issue. Voters who prefer the underdog can pick that candidate as their first-choice candidate in the confidence that their second-choice will receive their vote if the underdog candidate fails to gather enough votes to enter future rounds.