In Classical Greece, awareness of the different troop types available to the enemy was essential. The Greeks knew about the strengths and weaknesses of different troops; they knew heavy infantry couldn't fight light infantry, and that both infantry types were vulnerable to horsemen. They usually tried very hard to adjust the composition of their army to the kind of enemy they were up against. Take for example the recommendations of Nikias to the Athenians who were planning to sail for Sicily in 415 BC:

I think, therefore, that we ought to take great numbers of hoplites, both from Athens and from our allies (...) and great numbers also of archers and slingers, to stand our ground against the Sicilian horse.

-- Thucydides 6.22

Or the considerations of the Spartan king Agesilaos, when he was trying to fight the Persians in Asia Minor:

Perceiving that, unless he obtained an adequate cavalry force, he would not be able to campaign in the plains, he resolved that this must be provided, so that he might not have to carry on a skulking warfare [literally "fight a war of running away"].

-- Xenophon, Hellenika 3.4.15

As a result, Greek armies were always mixed forces in which different troop types played key roles at different times. We often get army descriptions like this:

Besides these [hoplites] there were Spartan horsemen to the number of about seven hundred, Cretan bowmen who accompanied the army, about three hundred, and, further, slingers of the Marganians, Letrinians, and Amphidolians, not less than four hundred. (...)

As for the enemy (...) this was the number of the hoplites; but as for horsemen, there were of the Boiotians (since the Orchomenians were not present) about eight hundred, of the Athenians about six hundred, of the Chalkidians from Euboia about one hundred, and of the Opuntian Lokrians about fifty. And of light troops also there was a greater number with the party of the Korinthians; for the Ozolian Lokrians, Malians, and Akarnanians were with them.

-- Xenophon, Hellenika 4.2.16-17 (Battle of the Nemea, 394 BC)

Those who were now drawn up against Agesilaos were [lots of hoplite contingents]. As for peltasts [i.e. javelin throwers], those with Agesilaos were far more numerous; on the other hand, the horsemen of either side were about equal in number.

-- Xenophon, Hellenika 4.3.15 (Battle of Koroneia, 394 BC)

Having become Tagos, Iason of Pherai assessed the contingents of cavalry and hoplites that the cities were to furnish, according to the ability of each. And the result was that he had more than eight thousand horsemen, including the allies; his hoplites were reckoned at not fewer than twenty thousand, and there were peltasts enough to take on the whole world.

-- Xenophon, Hellenika 6.1.19

Unfortunately, post-Classical sources are much less helpful. A Roman-era writer like Diodoros only recorded the number of heavy infantry and cavalry; he apparently didn't care to write about light infantry. From their work we get a much more primitive picture of Greek tactics than we do from the Classical Greeks themselves.