Hi Tomas,
I find the best way for me is to read comic books - the new words are backed up by pictures. I also then look them up in a dictionary online to double check the meaning. After that I try to make a sentence using the word - if only in my mind - and use it as soon as possible
I also watch movies in the language I am learning. New vocabulary will be in amongst words I already know. I stop the movie, look up the word and practice saying it in a sentence.
Let me know if that works for you!
Vicki