Synonyms and related words :
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