Know a handful of notes on sight — the line the clef is named after, middle C, the outside lines — and read everything else as one or two steps from the nearest one.
A mnemonic is serial: to find the fourth space you recite a sentence and count four things, and that costs about a second every time. A landmark is a single lookup, and the notes around it are then a glance rather than a count. Every rung of the stave is the next letter of the alphabet, so once you are anchored the arithmetic is trivial — the anchoring is the whole skill.
Mnemonics are still the right way to START, because you need some way to answer at all before you can answer quickly, and “Every Good Boy Deserves Football” gets you playing this week. The mistake is keeping them: they are scaffolding, and the sign it is time to take them down is that you can already recite them faster than you can read.
Estimate with the rule, then check it against the calculator that models it properly.
Open Reading Music →Know a handful of notes on sight — the line the clef is named after, middle C, the outside lines — and read everything else as one or two steps from the nearest one. A mnemonic is serial: to find the fourth space you recite a sentence and count four things, and that costs about a second every time.