Learning Words in Context
Studies show that we retain words better in context than as isolated vocabulary elements. Associate with each new verb you encounter or wish to learn two or three logical object or verbal complements.
For example: ankommen (to arrive): am Bahnhof/ mit Freunden/zu spät
OR:
schreiben (to write): einen Brief/einen Zettel/an Freunde
OR:
You could also write a complete sentence: essen (to eat): Der Junge isst einen Hamburger.

Review, Review, Review!
Studies also show that you retain things for longer and better if you review the topic, grammar issue, strategy, vocabulary.

Learn your vocabulary and practice the grammar structures!
You decided to learn a foreign language and you should take advantage of every situation that will provide you with exposure to German. Still, you will not learn by osmosis ☺. You will have to learn your vocabulary and practice the grammar. Once you have a good basis in both, you will rapidly increase your knowledge.