Four notes: R L R R, then its mirror, L R L L. The single paradiddle folds a single stroke and a double stroke into one phrase. Once you can play it cleanly, you can move accents around inside it, alternate hands across the kit, and use it as the foundation for hundreds of fills.
Why it's so useful: the pattern naturally alternates which hand starts each grouping, so over four reps both hands lead twice. That built-in balance is why drummers never stop reaching for it.
The Pattern
Sixteen 16th notes per bar, sticking R L R R · L R L L played twice through — four paradiddles, alternating which hand leads each group. Loop it.
Exercises
1 — Single Paradiddle on Snare
Sticking: R L R R · L R L L · R L R R · L R L L. The accents (the > marks above the staff) naturally fall on counts 1, 2, 3, 4 — the start of each paradiddle group. Let those notes be slightly louder than the rest. Playback sits at ♩=80; work it from ♩=70 up to ♩=100 once it is clean.