One question I get often deals with memorization, which makes sense. There is a lot of memorization in any subject, but especially with Japanese. New vocabulary and kanji are the two biggest examples I can give you. Thankfully this is a short post. To sum it up: I find a dual flashcards/sentences approach works very well for both instances.
The study of Japanese, in my experience goes from broad, simple concepts to more complex kanji and more refined and specific vocabulary and grammar. Some words or kanji might be near identical, but have certain nuances. This can double or even triple the amount of vocabulary very quickly. As a student, I started off very strong, but learning the nuances as I progressed started to become very difficult and I had to revamp my game.
Before I went to Japan, I downloaded a great app on my iPod, jFlash, which takes a lot from Jim Breem's JDIC (an online Japanese dictionary), a godsend in and of itself. With jFlash, you can create flashcard sets (for example, chapter 2 vocabulary, words which use the kanji "X") as well as use the app's own sets. The app does cost money though. It runs about $6.99 for the basic app and its additional entries and study sets. However, since it's portable and theoretically possible to create an infinite amount of sets. It also eliminates the need for a denshi jisho; it's definitely worth the expense of $7.
Writing I have always found to be very useful, especially with vocabulary. I sometimes have my students practice with constructing sentences to remember particle roles and placement as well as start creating more robust, complex sentences. By writing short, daily journal entries, you can practice grammar, vocabulary and kanji, which is all-around helpful. I recommend to do this manually, and if possible having a tutor look it over. I think some classes even require diaries or blog posts, which is a pretty cool thing; you can look back and see how far your skills have developed, spot on going trends of strengths and weaknesses. Failing that, subscribing to a site like Lang-8 gives you the chance to have someone check your grammar, but in my experience, sometimes the correctors dumb-down your sentences to something less ambitious, which is unfortunate. I'm experiencing this now as I progress into JLPT N1 territory, the grammar is ambitious and academic, but since many people are used to conversational Japanese, I get some weird feedback.
Kanji are a mixed bag for studying. You can get away with not knowing stroke order and the like, because typing eliminates the need to write them correctly, but knowing stroke order is essential if you're reading someone's chicken scratch. That said, many kanji are also more typically found in reading rather than reproducing, so flashcards are one way to go. I would recommend knowing how to read and write the kyouiku kanji (first 1000 taught in schools). When I was taking my second semester's required kanji class at Kanazawa University, the professor had us use a mix of writing the character about 30 times, memorizing a few common words and then writing a sentence or two using those words. It worked really well for me especially since I reenforced that method with flashcards, which did me well for recognition on reading in other classes.
As said before, I think that knowing how to write the kyouiku kanji is essential, especially since they encompass about 90% of all written material. The last 1000 make up about 8-9%, are less frequently occurring or part of specialized vocabulary. Just knowing the reading and meaning is best for those, as well as a few high-frequency words in those compounds, which brings us back to vocabulary (flashcards and sentences.)