Words are the building blocks of language, so one of the key tasks in Language Learning is to acquire more vocabulary. Of course, you will naturally learn words as you engage in tasks 1 and 2, but that process is much more random and less systematic by itself. Focused vocabulary acquisition can be an excellent supplement that brings a lot of consistency to conversation practice and comprehensible input.
Generally speaking, you should to spend your time using the language, and not studying it. However, words are so important that it's okay to take a small portion of your day to make sure you get them down in a more systematic way. No matter how much time you have to study your language, try to spend about 10% of that time every day focused on vocabulary acquisition, and then split the remaining 90% between conversation practice and comprehensible input.
Think of a new word in your target language like a corn plant that takes all summer to grow to its full height. Conversation practice and comprehensible input are like the water and sunlight that help the plant grow. Every time the word comes up in a book or in an online chat, you are forming a stronger bond with that word. But it's not always easy to pick up on new words that you've never seen before. That's why systematic vocabulary systems are like planting seeds. They create the first contact and draw your attention to new words that you might normally overlook. Planting seeds is not something you do all summer long, but it is an important first step.
In the next pages I'll outline exactly how I go about exposing myself to new vocabulary.