Since I've been working on languages so much since, well, high school, I figured that I would jot down some of the things that I've found have really helped my own language acquisition. These are mainly for written languages; spoken, contemporary languages would require a different take, I think, though these tips I suppose would work with them as well. These are not tips to make learning easier, mind you; they are tips to make learning effective and rewarding, once one gets serious about it.
In looking over the tips, I think that they mostly boil down to one thing: forcing yourself to actively learn details. Details are important in language learning, and I know that I hate learning them. So, the point of these tricks has been to put myself in situations where I have to think of the details, to train myself to notice them on a regular basis until they become second nature, and to find different ways of of doing this which reinforce each other.
- Use flashcards. This is a non-negotiable; you need to keep a lot of information in memory over a long period of time. You also need to have a system for reviewing flashcards on a regular basis, based on how well you can recall them. The best program I've seen yet for flashcards is Anki, and it's completely free and available for multiple operating systems. The next few points will deal with ways of using flashcards.
- When making flashcards, don't just make vocabulary items. Make full sentences illustrating grammatical points. For instance, I'll take Hansen and Quinn's Intensive Greek, or Coulson's Teach Yourself Sanskrit, or Wheelock's Latin and copy down a sentence or two for each section; I choose these books precisely because they offer plenty of example sentences. It makes remembering the different forms of, say, conditional sentences, or of the uses of the locative case, much easier. Plus, it makes you learn some vocabulary in context, which sticks much better than isolated words.
- Learn flashcards in both directions. You may only want to read the target language, but trust me, it helps tremendously to be able to go from English to Latin/Greek/Sanskrit/Arabic/etc. It forces you to pay attention to the details of the word; something which one-way flashcards overlook. For instance, I may remember that a given Hebrew word, qol has a given English meaning, voice, because I have no other Hebrew words yet in my vocabulary that start with q. This will let me pass my flashcard test going from Hebrew to English, but I do not know the word. More commonly, there are strings of words that look similar in the target language, and having to remember them from their English meanings forces me to distinguish between them; for instance, the Greek huphiemi, huphistemi, ephiemi, and ephistemi, all terms used often in Neoplatonic writings. Note: this tip doesn't just work for vocab flashcards; it is helpful for sentence flashcards as well. Sure, it's difficult, but it makes you internalize those sentence patterns, and that becomes quite nice when you are trying to make sense out of a difficult passage and need some intuitions to guide you.
- Make cram decks (Anki has a cram feature built-in). If you only cram the material, you'll never remember it, but the occasional cram on top of steady long-term usage can do wonders. First, it really helps when you input a bunch of new vocabulary items. You can't just remember the individual words, but you also need to see how they compare with the other words you will be learning, and a single cram session with the 100 words you need for the current chapter can help you make those interrelationships in a way that learning them 5 at a time will not. Don't worry about retention; just gun through them, expecting to get them all wrong at first. You'll start to recognize them in time, and a basic recognition is all you're going for. Also, the occasional cram helps with those languages which you haven't really been working on for a while but want to keep up anyhow.
- Speak the language out loud. Not only that, say it with feeling. This is an actual language you are learning, and it made (makes) sense to people as a language and not as a cipher for English. Pay attention to the little grammatical details as you emotively speak it, trying to make yourself feel the difference between, say, the accusative and the dative (I feel an accusative before its verb like a G 7th chord before a C Major, and subordinate clauses are like key changes, but that's just me). This will help you get a sense for the cadence of the language, and keep reading from being merely a parsing exercise.
- In line with the above, learn some poetry or something else fun. I have the first few lines of the Aeneid memorized, and occasionally when I am bored I'll recite them. But this isn't about rote memorization; again, the point is to pay attention to what the language means at every step, and a piece of poetry is something which I would have analyzed in detail at some previous time so as to be intimately familiar with how it fits together. Plus, poetry tends to be more complicated than prose, and so it gives a mental workout to a mind used to working with, say, Aquinas.
- Work through the language word by word. I have come across the idea that one should start working through a Latin sentence by looking first for the subject, then for the verb (or vice versa). This seems to me to be detrimental and silly. You look first for the first word; this is how it made sense to the original audience, and this is how it can make sense to you with some hard practice. The subject/verb searching should be reserved for cases in which you cannot make sense of the passage after having tried going straight through, or for when you want to double-check the meaning of the passage. Otherwise, hold each word in its full ambiguity until you find how it fits in the rest of the sentence. This requires some recognition of its semantic relations to the rest of the passage, and not merely syntactical. This article explains what I mean here.
- Read through a passage before resorting to a dictionary. This is most useful once you have reached an intermediate level and can recognize a decent amount of vocabulary, since (as above) the meanings of the words can be very important in determining how they fit in the sentence. However, once you have some idea of the vocabulary an author uses, make sure you try to read passages and make as much sense out of them as you can without resolving every single word. This will force you to pay more attention to the grammar and to context clues.
- Learn other languages. This tip won't work for everyone, but if you have the time, ability, and/or need, different languages can help reinforce each other. Learning Sanskrit has opened my eyes to all sorts of phonetic and morphological principles in other languages, because the Sanskrit grammarians focused so much time on this aspect of their language. Reading Classical Arabic has helped me to pay more attention to syntax; there are case endings, but most of these are unwritten ad so must be supplied from the context. I found that due to this practice in Arabic, I had absolutely no problem understanding German sentences even before analyzing all the noun declensions. Learning one highly inflected language will sharpen your grammatical skills in others, and the more vocabulary you have at your fingertips, the easier it is to form associations with new vocabulary items in other languages.