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!