I've only ever had / and swap. Seems to have worked out OK so far. Touch wood, fingers crossed, etc, etc...
Not very interesting /etc/fstab:

Have a shared /home but create a different user account for each distro. So your login name might be something like:

fred.suse
fred.slack
fred.redhat

And then use the user home folder for settings only. Create another folder (or even partition) for stuff which would be common to each account, such as documents, pictures, music and videos.

Multiple partitions for /home, /usr, /etc for multiple distros is not a big problem nowadays if you do your distro tryouts in VMs/containers. I use either Docker or libvirt/KVM for this.

The only directory that's somewhat still desirable to segragate though would be /tmp and /var (the former because you tmpfs it anyway, and the latter if you're putting databases onto "optimized" filesystem types.)

As I understand it, y'all refers to up to three individuals; all y'all refers to more than three (up to 100,000 in a football stadium or an auditorium full of country music fans for example). Depends on where you're at, too (varies somewhat by the section of the country).

OK, partitioning.

Easy way, one for root, one for swap and one for /home and you're good to go.

Harder way, one for root, one for swap, one for /home and any number to isolate stuff you don't want to loose on a fresh install; e.g., /usr/local, /opt, /var/lib/mysql, /var/lib/pgsql, /var/lib/virtual and so on (I use /var/lib just because Slackware installs MySQL/MariaDB in that tree and I'm good with that; I mount a partition or second drive to those points).

System software (at least Slackware system software) installs in root -- only root -- /bin, /boot, /dev, /etc, /lib, ... /sys, /tmp, /usr and so on. When I get a new release of Slackware, I do a clean install then add back any additional software that happens to get installed in the root tree (like SlackBuilds that I haven't edited to install in /usr/local which is where I really prefer they be).

It's not a big deal to do that. If you remember, during installation when you're adding partitions you have the option of formatting the partition or not. I format the root partition but I don't format any of the others (I have a lot of stuff on other partitions that I don't want to back up and reinstall if I can help it; big-ass data bases, big geographic data files, big a lot-of-stuff). I have four severs all configured identically (even though a couple of data base server have multiple drives, the mount points are the same on all servers).

I don't do the multiple booting you mention -- if I'm going to fiddle with different distributions, I fiddle with them in VirtualBox and they "live" in /var/lib/virtual (in one case a separate drive, the data base servers don't have VirtualBox installed, but the mount tree is the same). This avoids the complications of booting; VirtualBox (at least on 64-bit systems) is fast and, well, you don't screw anything up with multiple boot problems.

I also keep them "pure;" my data base servers are two Dell Dimension 8400's (oldies but goodies so far) which are 32-bit boxes and the dual-side DVD from Slackware makes that a breeze to do the above-described "clean install." And, that clean install takes about 20 minutes start-to-finish, up and running (I do keep a copy of /etc to get up to speed quickly using standard configuration files; e.g., /etc/passwd, /etc/shadow, and others).

This has worked for me through Slackware releases from, oh, heck, 6? I duuno, long time. And VirtualBox makes it easy to have a Windows virtual guest that I don't have to reinstall (I actually don't do "distro-hopping" because I'm perfectly happy with Slackware and have been for a long, long time; no reason to switch or fiddle around that I can see).

Hope this helps some.

Interesting thread. I used to use separate /swap, /boot, /, /home, and /usr but over time began to assess that for a SOHO system the problems outweighed any advantage at least for me. Now I just use /swap and /. and link major storage directories (ie: /home/foo/Downloads) in my various and changing distros to my main, and some, vice versa. I have read that some people prefer to isolate "/etc" on servers for backups though with rsync incremental I really can't see a major advantage.

Ya'll have given some good ideas (I actually grew up in Europe but hung around some kids from 'Bama).

I currently have:

/dev/sda1 on / type ext4 <-- this includes everything except:
/dev/sda5 on /opt type ext4 <-- I keep most additional programs here
/dev/sda6 on /temp type ext4 <-- loads and loads of junk
/dev/sdb1 on /home type ext3 <-- why is this ext3? I thought it was ext4...

I do it this way so I can wipe /dev/sda1 and reinstall if I want, without effecting anything in /home and /opt. Actually, as you can see /home is a different hard drive. I used to keep /usr/local on a different partition, and I may do that again because of all the stuff I have there.

I do not keep /boot on a separate partition. I can't tell you how many Ubuntu boxes I've ran across that won't install updates because there is no room left on /boot. After you get a half dozen or more kernel versions the /boot directory fills up and you have to manually remove old kernels.

The whole idea behind using different partitions for me is so that I can wipe the root partition without my data files or programs being effected. I can install a clean install of Linux and all of my settings, email, documents, etc., are there waiting for me because /home was never touched.

You know - you could just use quotas to achieve the same goal. Instead of having one partition for every file you have.

Years ago,I followed the latter partition scheme, and found it didn't work for me; on occasion, I might need to reinstall Slackware. In these cases, I personally think it's better to leave /home untouched, because then the install will leave my personal settings for KDE, vlc, .asoundrc (for ALSA), etc. alone. Also, separating my home partition from the root allows me to use LVM to aggregate two or more hard drives into one large logical partition, allowing room for future growth. This particular arrangement has suited me well since I first adopted it, and I see no reason to change now.

For reference's sake, my /etc/fstab: