Timing your visit
Go at opening time or in the last two hours before closing — midday, especially in summer, means both the biggest crowds and the least shade on an exposed hilltop site. Allow at least 2-3 hours for the Acropolis itself.
Tickets and the combined pass
A combined ticket covering the Acropolis and several other ancient sites (Ancient Agora, Roman Agora, Kerameikos and more) is usually available and worth it if you plan to see more than just the Acropolis, since it is valid across multiple days.
The Acropolis Museum
Located just below the Acropolis, this museum houses artifacts found on the hill, including original sculptures with glass floors revealing ancient ruins beneath the building. Pairing a morning at the Acropolis with an afternoon here is a natural, low-effort combination.
Budget a full day for the Acropolis, its museum, and a walk through the Ancient Agora below it — trying to rush all three in a couple of hours undersells what is genuinely one of the world's great historic sites.