The ancient sources for helots are of such paucity and quality that scholars keep getting to diametrically opposite conclusions about who they were, what was their servial status, and the timing of their servitude. If you're interested in Helotry, I'd recommend this collection of essays, edited by Susan E. Alcock and Nino Luraghi. It's a fascinating book and great because many of the authors hold completely contradicting views, reflecting how 'thorny' the whole topic is. Following is a brief outline of the basic facts that most academics (well, me at least!) agree with.

As the holy Oxford Classical Dictionary reminds me, other Greek states than Sparta had servile populations which were not privately owned douloi, but, because their status seemed superior in important respects, came to be categorized as ‘between free men and douloi' (Pollux 3. 83). When discussing non-Doric states, we might call them serfs etc.; 'helots' is specific to Laconia and Messenia. 'Helots' were thus not an oppressed ethnic group, but rather a term referring to a certain social class. Helots could be manumitted (although at least in Sparta, in only exceptional circumstances) and thus 'stop' being helots. Our best sources to helots are about Spartan helots - I cannot say to what extent the Spartan example can be generalized into other Doric city-states. In Sparta, helots had some property rights, unlike slaves (which weren't very common in classical Sparta, mind), and whereas slaves were always considered as a personal property of one individual, helots were sort of considered to be the property of the citizen community as a whole. Spartan helots had some military obligations, too, whereas slaves did not; their main responsibility, however, was to provide their Spartan masters and mistresses with a fixed quota of natural produce.

To answer your question, what do we know about helots before they were helots; not much, really. It is believed that the classical helots are descendants of those Greek peoples that the Dorians enslaved during the Dorian invasion, somewhere between the 7th and 10th centuries. The word 'helots' (heilōtai) is most likely derived from a root that means to capture, and the helots certainly 'enjoyed' the position of being ritually demeaned and considered as a sort of the 'enemy within' in the Spartan state (J. Ducat in his Spartan education stresses this 'ritual demeaning' of helots), on top of the very real fear of a helot revolt (e.g. Thucydides 4.80). Every year, the Spartan ephors ritually declared a war against the helots, and Spartans could guilt-free kill helots. The ancient sources suggest that this was to keep the massive helot population in check, which the ancient authors believed to by far outnumber the citizen population. Not that it made any sense for the Spartans to kill helots on everyday basis; the helots were basically the bedrock of the Spartan states as their main source of agricultural labour. The most famous example of the helot oppression is of course the infamous krypteia institution, which was an initiation rite for young Spartan men where they went to the countryside in groups to randomly kill helots with daggers (well, this is the picture Aristotle paints; e.g. Plato described it a bit differently).

Helotry survived as an institution well into Hellenistic era, and it wasn't the helots who freed themselves in the end. Helots survived as a self-perpuating body until Theban general Epaminondas freed the Messenians from the Spartan league in 369, and the remaining Laconian helots weren't freed until early 2nd century B.C. A revolutionary chap called Nabis seized the Spartan crown around 207 B.C., and he put under way some badly needed modernizations, including effectively ending the status of helots, and also the periokoi class of citizens was practically abolished later during his reign.

EDIT: spelling