When learning a new language, it is necessary to use the language everyday and study whenever you possibly can. For learning vocabulary, you could start by writing your "to do" lists in the language, or even giving commands to your dog. Label household items, like the table or television, with the word in the language. And start translating everything you see or read or hear into the new language. See how fast you can switch between the two (or more) languages in your mind.
One useful way to remember nouns (and their genders) is to associate them with other ideas that you are already familiar with. I will never forget that the Russian word for world and peace is mir because I thought it was so strange that one word could mean both of those things. I can remember that ausgezeichnet is excellent in German just because it's so fun to say. I know that la camera is Italian for bedroom because I took pictures of my room to finish up a roll of film a while ago. Le carré in French means square, and every time I see a book by John le Carré, I think his name is John Square.
You can also use this mind trick to associate words with other random things that will help you remember the vocabulary. The Dutch and German word for donkey is esel, so picture someone painting a donkey on an easel (that is, by the way, where English got the word for easel, although I have no idea what it has to with a donkey...). In Russian and Croatian, the word for home is dom, which is the beginning of domestic in English. Comprender in Spanish is to understand, and it's similar to comprehend; aprender is to learn, and it's similar to apprehend, as in apprehend the information and send it to your brain. The word for intersection in French is le carrefour because four cars meet there. Il corpo in Italian means the body because after it is dead, it becomes a corpse. There are numerous relationships to discover between vocabulary words and associated ideas. A little imagination may be necessary, but it sure beats making flash cards or writing word lists. That's not to say that flash cards are a total waste. Just make sure you write them yourself to get extra practice, and study them in every free moment you have during the day.
Do you want to talk with people around the world, are you interested in foreign cultures? Language Learning is a good thing then - if it just wouldn't be so exhausting.