Learning vocabulary for languages is both essential and difficult therefore developing easy techniques is extremely helpful when learning a language. I find little and often is the most effective way to learn vocabulary and I'll often turn it into a task that I would be doing anyway. Good examples of this are watching Netflix in German with English subtitles, watching the news in German and changing your phone settings to German. Apart from these, if you section off 10 minutes a day to learn vocabulary or even just set yourself 10 words a day and consolidate at the end of the week, you can learn lots of new words without too much work! Something I find particularly useful is the site 'Memrise'. If you are struggling to remember a word, then they give you tips and connections to the English translation that help long-term memory and learning.