1:1–8 (prologue); 1:9–3:22 (seven letters); 4:1–8:1 (seven seals; sometimes 4:1–5:14 is seen as a separate introduction); 8:2–11:19 (seven trumpets); 12:1–14:20 (seven signs? including 15:2); 15:1–16:21 (seven bowls).
One of the problems even with this outline is that the sections often termed “interludes” or “parentheses” are not delineated (i.e., 7:1–17; 10:1–11:14), and so some authors prefer to exhibit these separately as parenthetical, or as subordinate to, or even as a part of, the preceding sections.