Method 1 — Initial rates: Vary [A] while keeping [B] constant. If rate doubles when [A] doubles: order = 1 w.r.t. A. If rate quadruples: order = 2. If rate unchanged: order = 0. Mathematically: m = log$\frac{r2/r1}{log}$([A]_2/[A]_1). Method 2 — Integrated rate law: Test which linear plot works. [A] vs t (zero), ln[A] vs t (first), 1/[A] vs t (second). Method 3 — Half-life: $t_1$/2 independent of [A]_0 => first order. $t_1$/2 proportional to [A]_0 => zero order. $t_1$/2 proportional to 1/[A]_0 => second order. General: $t_1$/2 proportional to [A]_0^(1-n) where n = order. The initial rates method is the most straightforward for JEE problems.