Reading is usually considered the easiest part and it is so for a reason. Most learners are inevitably exposed to English texts and phrases. English is the most common language on the Internet and many sites don't offer any translations. Having said that, the ability to read says very little about your overall performance. Languages are redundant, so even if a sentence has several words that are unknown to you, you still can get an accurate idea of the meaning by looking at the context and guessing unfamiliar words.
Another passive skill is listening. Unlike reading, this one can be quite challenging, because we hear English speech less frequently than we read English texts. This underexposure can be fixed relatively easily, especially in the era of the Internet. Podcasts, news, TV shows and audiobooks are only a couple of clicks away. The simplest piece of advice for those who want to improve listening skills is just listen as much as possible. At first, you won't understand anything but eventually it will all become clear.
Most students see speaking fluently as the ultimate goal of the learning process. The problem is that without well-defined criteria, this skill is extremely difficult to assess. For example, let's take a look at business people who have to use English for communication. On the face of it, they may produce seemingly effortless speech and even appear proficient. However, quite often their active vocabulary is limited to a couple of thousands of words and they mainly use basic grammar. Moreover, since this is usually all they need, business people also lack motivation to improve. So, at the very least you shouldn't view them as good role models and aim much higher.
A brief look at IELTS statistics shows that students usually get the lowest band for writing and again there are several reasons for that. First of all, even those who spend a lot of time studying the language don't get much writing practice. Second, it is the only skill where correct spelling really matters. And finally, different countries often have different views on what is regarded as good writing. For instance, in English-speaking countries coherence and cohesion are almost essential in academic environment. On the contrary, in many Slavic countries it is possible to get a PhD without even knowing what these things mean. This skill is often neglected in favour of speaking but I personally don't recommend you to do so. The thing is, writing is still important and it's arguably the hardest skill to learn, so I suggest you start practising it from day one.
What is next
This concludes my second introductory article. If you haven't read the first one, I would suggest you take a look at it. Next time I am going to give an overview of the language aspects such as vocabulary and grammar and outline how they fit into effective learning process.