Firstly, the ENT specialist will ask about your symptoms and related medical information. Then he might do a scope to look at the turbinates in your nose. If he suspects or want to rule out sinus infection, he might order a CT scan for you. A CT scan can show if there's any infection in the sinuses and it shows as white patch on the film.
Antibiotics is good only if you indeed have sinusitis but if you have allergic rhinitis or vasomotor rhinitis, it will not be of much help. The common treatment for rhinitis is nasal steroid sprays. It has very much less side effects compare to those oral steroids. If your rhinitis is caused by allergies, anti-histamines will help you too and avoid your allergens. Do not be on long term decongestants sprays as it can have a rebound effect.
I had surgery done to remove part of my turbinates and bone. Medications didn't work for me. I even bought dust mite protectors and I still got symptoms and they were just getting worse even I was on medications, both oral meds and nasal sprays.
You mentioned that your mucus is clear which is more like allergic or vasomotor rhinitis. If your sinus has infection, the mucus should be something like yellow or green. That's what I think it should be.