Tuning by ear
You have a tuner. You also have four open strings, and those are a better teacher — because they tell you not just a right pitch, but whether your note is in tune with your instrument, which is what actually makes it ring.
The trick: listen for the beats
Play a D on the A string (3rd finger) while the open D string sounds underneath. If your D is slightly out, you'll hear a slow wobble in the sound — a pulsing called beats. As you inch the finger toward the true pitch, the beats slow down. When they stop completely and the two notes lock into one clear, ringing sound, you're exactly in tune.
It works for any stopped note that has a matching open string an octave away: a G on the D string (3rd finger) against the open G below; an E on the D string... anywhere your note and an open string are the same letter.
The perfect 5ths between your open strings — G–D, D–A, A–E — are the other place you hear this: you tune the whole violin by playing two open strings together and listening for the beats to disappear. Octaves and fifths tune cleanly by ear, which is another reason they're called "perfect."
The drone is the same idea, held
The drone bar is this feedback loop running continuously. With a D drone on, every note of the D scale is being checked against home as you play it — you hear immediately when ^3 or ^6 drifts. This is how sargam is practised against a tanpura, and it's the fastest way to build reliable intonation.
Thirds are harder
Tuning a 3rd or a 6th by ear is trickier — they can sound very slightly different depending on the tuning system, and a violinist actually chooses where to place them (higher for a melodic leading tone, a touch lower inside a chord). That's a real thing, and it's the lesson In tune is not one thing. For now: use the 5ths and octaves as your anchors, since they have one clear right answer.
Try it
Try
Play a one-octave G major scale, slowly, and after each note that matches an open string — the D (^5, against open D) and the top G (^8, against open G if you can reach the open string, or just hear it in your memory) — pause and check for the ring. Adjust. A scale practised this way, listening for resonance, trains your hand where every note lives.
The usual mistake
Living by the tuner, or by finger-tapes, and never developing the ear underneath. Tapes and tuners are scaffolding — useful at the very start, but the goal is a hand that finds the note and an ear that confirms it. The open strings do the confirming for free, every time you play a matching pitch.