I grade every decision against a position chart preflop, and against your real equity versus these specific opponents' ranges postflop — then tell you what drove the answer.
To call a bet of B into a pot of P, you need to win at least B / (P + 2B) of the time. Call 20 into a pot of 60 → you need 20/100 = 20%.
To count your equity fast: multiply your outs by 4 on the flop (two cards to come) or by 2 on the turn. Nine flush outs on the flop ≈ 36%.
Those two numbers decide most calls. Everything else is a refinement.