SSD boot and home folder

It really depends on what you want to do and whether this machine is used by a single user, or multiple users with multiple media folders (music/movies/pics etc) and if those users want to share a single source of music/movies/pics or each have their own...

Since 256GB is a reasonable size and there is an advantage in keeping things simple and keeping some user files on the fast SSD, the way I would do it would be as follows:

Make a clean installation on the SSD and include the /Users directories on the SSD which is the default. This will mean that things like the web browser cache are on the fast SSD and not the slower HDD.

Your ~/Library should remain on the SSD.

Then I would format the HDD with a suitable Volume name like "Media" and then it should be mounted (by default) on:
/Volumes/Media

Now create folders on the HDD for those large media libraries such as Music, Movies, Pictures. Of course you need to make sure that you create those folders with correct permissions so that you can read and write to them!

Then create symbolic links for those large media libraries such as Music, Movies, Pictures so they appear under your home directory. You can also move 'Downloads' to the HDD (and link it) since that doesn't need high speed either.

 

I used Carbon Copy Cloner to copy my user folder to a separate volume (by only ticking the user folder to copy). Create an account in Users & Groups preference pane (I called mine 'admin') then log out of your account and and log into the admin account. Then go back to Users & Groups and right-click on your main user account, which brings up 'advanced options'. Now all you need to to is, next the Home Directory entry, click 'choose' and point to the new user directory that you have copied with CCC. Log out, log back into your main user account and you're done.