Pen and paper
Still the most common system, and for good reason. It's fast, it's free, it never needs charging, and nothing about it gets between you and your client. Plenty of fifteen-year teachers still keep an index card per client.
Where it runs out: it only holds what you write, and you write it after the session, from memory, usually tired. You can't search it, you can't send it to anyone without taking a photo, and a progress report means flipping back through months of cards.
A Word or Google doc per client
A running doc is a real step up. It's searchable, it's backed up, and you can copy a section into an email when a client asks what you worked on. Many instructors keep one long doc per client with the newest session at the top.
Where it runs out: it's still typing after every session. Notes aren't five minutes, they're fifteen, times eight clients. When the roster fills up, the doc is the first thing to fall behind, and a doc that's three weeks behind is worse than a blank page because you stop trusting it.
Notes in your scheduling software
Most booking and scheduling platforms have a notes field on the client profile. The appeal is that it's already open: the client's name, their booking, and your notes all live in one place.
Where it runs out: those fields are built for admin notes, not session notes. They're usually a plain text box, so a real session record (exercises, springs, sides, modifications, cues) gets squeezed into a sentence or two, if it gets written at all.
A class planning app
Class planners are genuinely good at planning. You get an exercise library, often with video, filters for apparatus and level, a drag-and-drop builder, and a way to read your flow off your phone while you teach. If the hard part of your week is choreographing group classes, a planner will save you real time. Some will even suggest a flow for you.
Where it runs out: a planner holds the plan. When you adjust on the fly, and on a private session you always do, the app still shows what you intended. The session itself isn't recorded anywhere unless you go back and edit the plan by hand.
Remo
Remo doesn't plan. It listens. You put your phone down, hit record, and teach the way you always do. Remo turns the session into notes: the exercises in the order you taught them, in your own words, with springs, sides, modifications, and the cues and corrections you gave. It also maps the session with a muscle heat map and a spinal motion chart, so you can see at a glance what you worked and what you didn't. It's a strong read, not a perfect one, and everything is editable.
Because the record builds itself, everything downstream of it gets fast. Before a session, Remo summarizes your last three sessions with that client so you walk in knowing where you left off. After, you can email the client a copy of their session in about thirty seconds. When you're away, a substitute brief (their intake, body map, and up to three recent sessions) goes to the covering teacher in a couple of minutes instead of an evening. And when a client asks whether they're getting anywhere, a progress report on any of their goals is one click.