- Don't wait too long before you start practicing. Most people find it uncomfortable to speak a language poorly and avoid it. Don't think you will wait until you're "ready".
- Going from zero to 100% will require some preparation. About 25 - 50 hours are enough for a European language, 100 hours for harder Asian languages.
Prior preparation is not essential if you're traveling to the country and going 100% from Day 1.