If you are the net control station of a daily HF net, what should you do if the frequency on which you normally meet is in use just before the net begins?

A fundamental principle of amateur radio is that no individual or group owns a specific frequency, regardless of how long or how often a net has met there. All operators have an equal right to use the amateur bands. If a frequency is already in use, the net control station should politely ask the current occupants if they would mind yielding the frequency for the net. If they decline, the net control must act courteously by finding an alternate clear frequency nearby and directing net participants there. Increasing power to intentionally talk over existing users constitutes malicious interference.