With globalization, cross-cultural competence is increasingly important to effective policies in international relations, business, and even in our schools and communities. Can we assess the skills and attributes relevant to gaining proficiency in other cultures? What kinds of training can help people toward this goal? Evidence on the assessment question comes from surveys of immigrant acculturation and expatriate adjustment, investigating antecedents including personality, general intelligence (g), and social-cultural intelligence. Evidence-based research should guide organizational and public policies for selecting people for intercultural positions, assignments, and assistance. Although past assessment tools have often lacked the validity necessary for consequential applications, recent innovations make the implementation of these policies feasible. Evidence on the training question comes from research on multiple learning processes that play different roles in the journey toward proficiency in another culture, such as studying, attributional reasoning, social learning, and conditioning. Training policies should recognize the distinctive demands of each learning process and identify evidence-based training procedures that fit the learning process. Finally, parallels across the two halves of our discussion on assessment and training can help understand both how personality traits and social strengths foster intercultural learning, and why general mental ability is not as important a driver as many assume.