This article is devoted to overviewing several current studies on L2 vocabulary learning, especially those aimed at investigating and exploring the ways in which deliberate vocabulary learning would be best facilitated, and thus would increase learning. It is argued that knowledge of vocabulary is fundamental in all language use, and becomes an essential part to master second language. A large amount of vocabulary is required to use English both receptively and productively: 8000 -9000 word families needed in order to adequately comprehend a wide range of written discourse [19], and 2000 -3000 word families required to get sufficient comprehension of spoken discourse [25]. Knowing a lexical item entails several aspects of word knowledge i.e., form, meaning, and use, each of which is further comprised of several sub-aspects of word knowledge. In addition, vocabulary learning is incremental in nature. Taken all these into account, there should be a component of deliberate vocabulary learning in language teaching, regardless of the preferred teaching methods being applied. Most importantly, deliberate learning of vocabulary should be intensively focused on lexical items which fall into both the new GSL word list [1] and the new AWL word list [4]. Finally, reviewing current studies on L2 vocabulary learning results in several research-based guidelines for deliberate or intentional vocabulary learning which are discussed throughout the rest of this article.