Hi, Emma =)
Well, I think that there isn't a best method that works to every one, there will always be one method that can work better to you than to me. But I will tell you what's been working the best for me :)
If you are starting to learn a new language, it's nice to begin with the basic, like : alphabet, greetings, numbers, days of the week, months, colors, food, objects, personal pronouns, then go to some adjectives, verbs, how you build a phrase correctly, time of the verbs and so on...
You can retain new vocabulary by stating to yourself a goal, like " I will learn 3 new words per day " or even one, and you will get to know word and how to use it :)
Later on when you feel ready to have some conversation, you can find a language partner that can help you with the pronounciation, you will be practicing and learning new vocabulary as well .