This school year, the last year of classes for my Ph.D. program, I am adding one more language to my inventory: Arabic. The class is a combined grad-undergrad class, so it is moving pretty slowly. Just as well, considering all the work I have to do for my three heavy-duty classes. Although I am no expert on Arabic yet, I have found a couple of useful study tips. Actually, they are useful when studying any language, though the details will vary.
Specifically, when you are learning verbs, learn all the principal parts for each from the very beginning. In Arabic, these are the perfect, the imperfect and the verbal noun. If you don't learn all of these from lesson 1, you will get to lesson 11 and suddenly find that you have to learn a long list of verbal noun forms for all the verbs you have already covered. And if you don't learn the imperfect forms, you'll have all those dumped on you in lesson 12. (These lesson numbers are from Wheeler Thackston's text, but the principle applies regardless of which book you are using.)
When learning nouns, you need to learn the singular and the plural. Some nouns have two plurals: "sound" and "broken." Some have just one or the other. But if you don't learn them from the beginning, you will presently find yourself presented with a long list of plurals to memorize.