Start at the speed you can play cleanly
Set the tempo to whatever lets you play the passage correctly, even if that feels embarrassingly slow. If you make a mistake, you are above your current ceiling โ drop ten beats per minute and try again.
The point is not to reach the target tempo today. It is to play correctly often enough that the correct version becomes the habit.
Count or clap before you touch the instrument
One bar of counting aloud tells you more about a rhythm than ten attempts at guessing it. Clap the pattern first, then play it, then play it with the click.
If you cannot clap it accurately, your hands have no chance of playing it accurately.
Raise the tempo in small steps
Once you can play a passage three times in a row without a mistake, add five beats per minute and repeat. Larger jumps reintroduce the errors you just fixed.
Work the transitions rather than the whole piece. Most mistakes live in the two beats around a chord change or a position shift, not in the notes either side.
Use the accents and the time signature
An accented first beat tells you where each bar starts, which is what stops you drifting a beat ahead during a long passage. Change the time signature to match your piece so the click lands where the music breathes.
For a quick tempo check on a passage you already know, tap along with the tap-tempo control rather than guessing a number.