Before transmitting, the first thing you should do is:

The absolute golden rule of amateur radio is to listen before you transmit. By monitoring the frequency silently for a few moments, you ensure that you do not accidentally step on an ongoing conversation that might have paused briefly. If you just transmit an announcement or ask if the frequency is in use immediately, your transmission might interfere with a faint signal or a station in the middle of a transmission gap. Only after listening carefully for a reasonable amount of time should you transmit to ask if the frequency is occupied. Listening always comes first.