How do I sing un-nasally?

My school teacher tells me to "lift the soft-palate and use an imploded k". I sounded "un-nasally" for a few weeks. However, my singing teacher tells me that I'm singing with a tight throat. When I try to lift the soft palate, I tighten my throat. Today, in singing class, I sang without the "tight throat" and sounded non-nasally. However, now, I sound nasally again. How do you know when your soft-palate is up? How do you know if you're singing nasally or not? How can I be 100% sure that i'm never nasally?