Single sideband (SSB) is the standard voice mode on HF. It is AM with the carrier and one of the two sidebands removed, so the only thing transmitted is the voice itself, in about 3 kHz of spectrum. All of your power goes into speech, which is why SSB reaches farther than other voice modes on the same power and fits more stations on a band.
SSB drops the carrier and one sideband: half the width, all the power in the voice.
Whether the voice sits just below the carrier frequency (lower sideband, LSB) or just above it (upper sideband, USB) is convention, not law. By habit: LSB below 10 MHz, USB above, and USB on VHF and UHF. In the US, 60 m is the exception where USB is required.
Low bands LSB, 14 MHz and up USB. Habit, not law.
Both stations should use the same sideband. The wrong one sounds like unintelligible mush.
Tuning a signal in
SSB sends no carrier to zero in on, so you tune by ear: nudge the dial until the voice sounds natural. Off by even 100 Hz, speech sounds too high or too low ("Donald Duck"), because every pitch shifts by the same number of hertz. The RIT (clarifier) fixes this on receive without moving your transmit frequency.
Ghost lines: how the voice should sound. Solid lines: what you hear.
You hearToo high
The dial shows where the suppressed carrier would be. An LSB signal extends below that number and a USB signal above it, so near a band edge keep the whole 3 kHz inside the band.
Operating
Listen, then ask. "Is the frequency in use?" and wait. Then call "CQ CQ CQ, this is W1ABC, W1ABC, calling CQ and listening," with your call sign in phonetics.
Answering. Give their call once, then yours.
Breaking in. At a pause, give only your call sign. Don't barge in.
Don't overdrive. Too much microphone gain flat-tops the audio and splatters across neighbours. Watch the ALC meter; see Mic gain, compression and ALC.
Leave room. Keep about 3 kHz between conversations, and never tune up on a busy frequency.