I tried to use flashcards and vocab apps, but I lose interest so quickly! For me, I like to read books. While I read, I have a lot of mini post-its on hand, and I put a post-it on each page and write down all the vocab I don't know. I love reading, and there are many great foreign-language books out there. I use Thriftbooks.com because I can get used French books for a few dollars even when they're hard to find elsewhere. Then when I reread the book, I have those notes for reference. I also notice that some words have trouble sticking in my head because I'm writing them on the post-its over and over! 

Right now I'm using Memrise to increase my vocabulary in Spanish. It's fun :) also I used "mi vida loca" by BBC before; they are short videos that makes you take part in them and memorize new vocabulary.

My method is learning by heart each word than tell a story about this word. I won't forget it with this method

I think reading is the best way to learn vocabulary

I find it useful to put up Post-It notes around your room/home of vocabulary words for each item. For example, on the window put a note that says "la ventana", or, on the door put "la puerta"...You get the idea. This way every time you go into your room, the vocabulary for those items is reinforced. The downside is that it only really works for household items, but it's a start!