THESAURUS
advertent, agog, alert, all ears, all eyes, apt, assiduous, attentive, aware, careful, concentrated, conscious, decisive, diligent, earnest, expeditious, finical, finicking, finicky, heedful, immediate, instant, instantaneous, intense, intent, intentive, meticulous, mindful, nice, niggling, observant, observing, on the ball, on the job, open-eared, open-eyed, openmouthed, prompt, punctual, quick, ready, regardful, speedy, summary, swift, watchful
