(1) what is the best way to make discs of audio files: CDs or DVDs, or something else?
(2) Other than sending discs to friends, what is the best way to share audio files on the Net? YouTube and similar sites are good to share videos but are their equally good ways to share audio files on the Net?
It depends what you want them for. If you want to be able to play them on normal audio CD players, then Audio CDs are the only real option. For backup purposes, an external hard drive is probably better. For archiving on optical disk - probably data CDs with flac format files.
Uploading to your own web space and posting/emailing a download link is one of the most efficient and convenient. Works best with web space that you have ftp access to, then you can upload with an ftp client program such as Filezilla, or the FireFTP plug-in for Firefox. Your friend can download using either ftp or just a normal (http) web link.
Drop IO offers 100Mb free file sharing “drops” (no horrible adverts): it has an inbuilt audio player so you can hear before you decide to download e,g,
Other file sharing sites are available, some are also free but have nasty adverts for casinos etc, others are ad-free but rquire a subscription.