What can cause someone to get dizzy?

Many things. "dizziness" can be caused by low blood pressure, sinusitis, viral infection, ear infection, meniere's disease, a stroke or tia, brain tumor or other CNS process, or "idiopathic" (no discernable reason). If the symptoms are persistent or severe, you should see a physician.
Vague symptom. "dizziness" : vague symptom; can mean lightheadedness, sense of impending faint, dysequilibrium (unsteady gait), vertigo (spinning: either you or the room). Does it vary with position, head change, bending down, standing up, nausea, visual, hearing changes, ringing in 1 or 2 ears, palpitations try to pinpoint what you notice, so when you tell the doc, appropriate evaluation and rx can be given.