We went with a tour and the path was very clear. I'm not sure that you can go without a tour, and I probably wouldn't suggest it because they drive you there, guide you up the mountain, and give you a ride back for very cheap ($5 to $10).
The hike is tough, although for part of the way they will offer you a donkey. Also, near the top they ask who wants to continue on, and some members of the group chose not to. Towards the top, your feet sink in volcanic ash, so it is difficult to step. Also, the air gets thin, making it difficult. It is well worth it when you get to the top. Getting to the crater is very cool and you feel a real sense of accomplishment.