Mail-in sounds awfully convenient, but we don't have it here for everyone. I believe senior citizens may have an automatic right to vote absentee, and that anyone else who can show they're going to be out of town or they live overseas or something can request an absentee ballot in advance. I've never done it myself, but I have one friend who has lived overseas for decades and still votes here (absentee by mail) because it was her last US mailing address. I would imagine the same might be true of military or other expats.
We do now have early voting in person, at a reduced number of central locations, for about a 2-week period before the week containing the Tuesday election day. If I recall correctly, something like 30 to 40% of voters choose that option, especially in primaries, where turnout tends to be otherwise low.
In my city we do have electronic/computerized voting machines, and have had for a decade or two, though I think they may now be required to produce paper backup copies as a security measure. There's a little wheel that you turn to highlight an option, and then a button you punch to record it, and another button with arrows to move around the page; you can go back and forth and make as many changes as you want, and it gives you a nice summary at the end before you finish.
The electronic system has always felt a little fishy to me, though, because they give you a unique PIN when you sign in to vote, and you have to enter that number with your ballot, so it seems to me that theoretically they could look up who voted for whom pretty easily. But hopefully they're not allowed to do that. I've also read that electronic voting systems are in general not particularly secure against hackers, or at least weren't in the first few generations of machines, many of which are still in use -- though as with impersonation of individual voters, I'm not sure there have been many actual cases where anyone has been caught trying to hack the system.
Before the machines came in, we did use paper ballots; I think they just had boxes to put an X in, rather than chads to punch or ovals to pencil in like on standardized tests, but I really don't remember in detail. Much longer ago than that, I still remember going as a small child with my mom to vote, and how she would go into the booth and pull the curtain, and then push the mechanical levers over next to each name. Sometimes she would point to a name and let me push the lever; it took a fair amount of force. I remember being astonished when she explained to me that the lever that opened the curtain also made the vote final. That seemed odd to me -- what if someone just opened the curtain to look for their child, or to ask a question, and poof, they had finished voting even if they weren't finished?
Later I was also surprised to learn that voters in some countries had to dip their thumbs in ink or have their hand stamped or something to show that they had voted, so they couldn't do it twice. As primitive as that seemed, I suppose it would also be a measure against fraud -- it's just not the custom here, any more than being required to cast a vote is. Or voting on Sunday -- that might make it easier for a lot of working people, but I doubt the churches would support it.
I still remember when the first elections were held in Iraq after the war, and how there were pictures on TV of people dressed up in their best, bringing picnics as if for a holiday, standing in long lines, but smiling and smiling, despite the armed guards and the worry about bombs and whatnot. That moment seemed so hopeful.
Turnout is a tricky issue. Apparently the US has a relatively low rate, especially among younger voters. I rarely feel like my vote has any chance to change anything, since I live in a state that's anything but swing, but mostly, I'm still motivated to go, or at least, I would feel bad if I just blew it off. If that marks me as passé, so be it. \-: