Taking IELTS and scoring high bands can be challenging(even for a native speaker), especially in speaking and writing(IMO writing is the most difficult section). This is primarily due to the rubric that is used to give you a score in speaking/writing(e.g. it's not enough to just be able to speak, you need to stay on the topic, use various vocabulary/gramma etc.).
I took General IELTS two years ago. Got 7.5 in everything except reading(where I scored 8.5). A colleague of mine had 9 in reading and listening, so it's totally possible, just requires more practice and concentration during the exam.
0) Learn about IELTS and how it works. Come up with the strategy that is going to work for YOU. For example I can recommend spending some time watching/listening to this guy: https://www.youtube.com/user/EnglishRyan
1) For reading / listening sections just drill them until you constantly score 90% or higher. Try doing academic readings, after doing them you will have no problems with general texts(always take a new sample reading/listening and work though it making sure you finish in time). I spent at least a couple of hours during each of my weekends for 3 months before the exam just doing the drills.
2) For speaking you need to have practice. As much as possible. Ideally with a teacher or a native speaker. If not possible, spend time reading English out loud, talking to other students, your friends or your cat.
3) Writing is really difficult. Most people have the lowest score here. EnglishRyan has some good info on his channel that can point you out in the right direction. However, the key here is that you will need to write a lot of essays(take a question from a sample IELTS test and write what is asked of you) AND make sure a professional teacher specialized in preparing to IELTS checks your writing and gives you feedback. I remember writing(and having assessed) at least 20 of those.