I have already said that we can reconstruct much of their culture by comparing the descendant cultures. We can also use the language -- if they had a word for something, they must have had the thing. (Unfortunately, we cannot do this the other way round; we cannot assume they didn't have a thing just because we don't have a word for it. The word may simply not have survived in enough language branches to be reconstructed.) We know, for instance, that they had the wheel -- *kw(e)-kwl-o-. We know that they had houses with doors -- *dhwer-. Many other things about their culture can be reconstructed this way. (For a good summary, see the appendix by Calvert Watkins to the American Heritage Dictionary.)
When all of it has been summed up, my guess is that they had what is called a transhumant culture. In such a culture, the main form of livestock, cattle in the case of the PIEs, is brought to summer pastures when the weather gets warm. There it is watched over by the young men, while the older men, women, and children stay at the homestead and take care of the crops that had been planted before the cattle had been taken away. In the fall, the cattle come home, and the whole tribe is together for the winter. I base this on a number of factors, including such an economy in such diverse areas as Iron Age Ireland and modern day Kalashastan. There are also certain cultural markers such as a tendency to think of things in pairs, indeed, in certain pairs, that marks such a culture.