Actually, any way you come to couples therapy is a good idea. There is a lot of research to support that. There was even an article in Consumers Report years ago that reported how couples therapy worked pretty well. But the best way usually is for you both to go together, to know what you and your partner are both doing and thinking, and to know what the couples therapist is saying to you as well as your partner.
If you can’t get your partner to go, it is just fine for you to go, if you are going to work on the relationship, work on changing yourself, work on seeing how things that bother you about your partner are related to you and what you do. It is fine to also go to relationship counseling alone if your intentions are to complain about your partner, expect your partner to change, and think that you are not the problem. But if you do that, you are most likely going to be using the relationship therapy to get out of the relationship. Just so you know.
You can always go alone the first session. It might be a good idea to have your partner go alone one time also if you do that. But are you deciding to go without letting your partner know? Unilaterally deciding? You can, of course, do that, but what are the consequences and meanings of deciding to work on the relationship without letting your partner know? It would be important to look at that.
So one issue that is coming up in this article: what is your intention for doing relationship therapy? And are you doing it alone or together and what might that mean? Worth thinking about. And couples therapy is worth it with a qualified, experienced therapist, to look at making each of you and the couple healthier.