We don't really know. The specifics of the lives of laborers and farmers and, honestly, nearly everyone, are scarcely recorded throughout history in general, and it's even worse when you get to something as old as the Pyramids. Which are astonishingly old. They were old like the Roman Empire is old, back when the Roman Empire was new. The trouble, you see, is that to know something like that you need records, and (1) most people didn't make records, since they couldn't write, and (2) if they did, those records don't survive well, being written on perishable materials. What we do know is written by the Big Men in the Big House (the literal translation of "Pharoh") because they could write and they occasionally decided to do so in stone, literally so that posterity would remember them. Mission accomplished, right? Actually, it's taken quite a lot of detective work to figure out even which kings commissioned the Pyramids, much less who built them and under what circumstances.

So, problems of historical knowledge aside, what do we know about the people who actually built the Pyramids? Herodotus tells us that he was told they were built by 100,000 slaves in three shifts, and that's been the typical idea of the builders until fairly recently. How much can we trust his report? Not much, being 2000 year old hearsay when he got it. He gets an awful lot wrong about all sorts of stuff.

So we start at 100,000, but archaeology and experiments and calculations keep bringing the number of pyramid builders down. We've found the towns the inhabited, and even some inscriptions they've made. It seems that 30,000 is now a quite comfortable estimate, and some will even go as low as 10,000.

When you have Herodotus' 100k (or 300k, depending on how you read it) it's hard to imagine anything other than some sort of forced labor. At 10k you can start to wonder if some really significant percentage of the corps was professional.

The social organization of the builders may have been slaves (perhaps captured in war) or corvee labor (a form of tax via labor) or paid craftsmen. Or, more likely, some combination thereof. Recent conceptions lean towards mostly some combination of the latter two, with a core of paid year-round professionals and rotating unskilled more-or-less forced labor. This seems reasonably supported by the evidence, though again, we don't really know.

So: If you were enslaved or paid, well, the answer to your question is pretty obvious. It gets more complicated if corvee labor is involved. This is an obligation of "the people" to work on the king's projects for some portion of the year. We presume this portion of the year is during the Nile flood, when there's nothing much to do agriculturally (and nearly all the people are involved in farming somehow.) So basically, the whole country's just sitting around for a while, might as well grab some of them for your pyramid (and other projects), right?

How are these people chosen? We don't know. It's fairly common, however, to see taxes as community obligations, simply because it's much easier administratively to keep track of a village's obligations and payments than of individuals. So most likely the regional administrator is given a number of "recruits" he must provide, and in turn tells each village how many people he wants from them. Then the village figures it out somehow, based on some combination of tradition and negotiation.

It could be that working for the king's afterlife project is quite attractive; it's a big patriotic honor. As a shirker, you just don't push to the front of the line, a couple of the big strapping youths of the village are sent off on their adventure down the Nile, and everyone's happy.

It could be that it's just another boring part of life, and you draw lots, or it's your turn this year, or whatever. If you're selected, maybe that's it, or maybe you can find (or pay) someone to take your place, or have a word with the elders that, man, the farm really needs me this year, c'mon, man.

It could also be that your village doesn't much care for the pharoh, who is basically a foreign despot. But if the village doesn't provide, they might send the soldiers over and, you know, burn the place to the ground and kill everyone. In that case, if you're selected, they're going to make sure you go. So I guess maybe you could run away and make them send some other poor guy. Though I don't know where you're going to go, and you'll be leaving literally everything behind.

I shouldn't be surprised to find all of these modes. And more. There's lots of people, and lots of time, and lots of variety in the human experience.