I've written about what to expect if you go for counselling, but one common misconception deserves a post of its own.
Counsellors do not give advice.
Or at least any safe, ethical and well-trained counsellor doesn't.
This is such as important value in counselling that it's written into the code of practice or ethical framework for just about every professional body in existence. Counsellors believe in respecting and nurturing the autonomy of their clients. The person who knows you best is you, and no matter how long a counsellor spends with you they will still only discover a tiny fraction of what makes you who you are. To function and grow as a person you need to develop the ability and confidence to make your own decisions.
Each modality approaches counselling differently. Some counsellors are more directive than others, and you'll need to do a bit of research to discover what will suit you best. Purely person-centred counsellors are unlikely to even ask you any questions in your sessions because they consider this to be imposing their agenda on you. Counsellors following other modalities are likely to ask things and maybe even offer several different perspectives - but they should never tell you what you must think or which decision you should make.
Perhaps you're unhappy in your relationship and you decide to try counselling in order to clarify your feelings and thoughts about this. Maybe your aim is to come to a decision whether to stay with your partner and work on the relationship, or to end things and go your separate ways. Only you can make that decision. If a counsellor listened to you and then told you what they believed you should do, that would be extremely unethical. They are not the one in the relationship, and they are not the one who has to live with the decision. Naturally they will form an opinion based on what you've told them, but they will know that this is only one perspective - and an edited version at that.
If the therapeutic relationship between you are your counsellor is well developed then you may be at a stage where they can be quite challenging, and you feel safe enough to be challenged. They may have noticed a pattern of behaviour on your part which you hadn't picked up on or you'd deliberately ignored because you know it isn't helping you. Gaining awareness of this may be painful or embarrassing, but it also gives you the choice to change if that is what you would like to do. Giving advice takes that choice away.