decimatio was not very common in any Roman period, but every Roman soldier knew what it was. Polybios wrote a bit about it:

The tribune assembles the legion, and brings up those guilty of dissertion, reproaches them sharply, and finally chooses by lots sometimes five, sometimes eight, sometimes twenty of the offenders, so adjusting the number chosen so that they form as near as possible the tenth part of those guilty of cowardice. Those on whom the lot falls are bludgeoned to death [...]; the rest receive rations of barley instead of wheat and are ordered to sleep outside the camp on an unprotected spot. As therefore the danger and dread of drawing the fatal lot affects all equally, as it is uncertain on whom it will fall; and as the public disgrace of receiving barley rations falls on all alike, this practice is that best calculated both the inspire fear and to correct the problem.(6.38.2-4).

There are only a few known cases of its use. Livy (2.59) mentions the punishment after the army of the consul Appius Claudius refused to fight the Volscians. Suetonius (Aug 24) mentions off-hand that Augustus did it to some recalcitrant veterans. The most famous is probably the incident with Marcus Licinius Crassus (the triumvir), who was sent to fight the slave revolt under Spartacus. His legatus with two legions lost a battle against the gladiator king and the legionnaires panicked, leaving behind their equipment in the process. This gave Spartacus weapon upgrades and supply and was generally not very good. Crassus was furious and ordered decimatio for 500 of the worst offenders (so 50 dead total)(Plutarch Crassus 10). This seems to have been the first time the practice was used in a century or more.

edit: the internet is filled with nonsense about decimation. For a reliable source, see Goldberg, "Decimation in the Roman Republic," The Classical Journal 111.2 (2015).