Probably many answers, all correct, but I'm wondering if you share LOTS of pics with clients (of whatever sort), or just YOUR selects, and how you do it - via a web album (flickr work?) or sending them a DVD or USB drive, or ... ?
Probably many issues I haven't thought of, as I haven't done this before ...
Our wedding photos came on a DVD with everything she'd shot, because we paid for the reproduction rights.
Not every photographist would do that, and was part of the reason she got the job.
Dropbox or custom password protected galleries on a website seem to be the usual way.
Usually web album on SmugMug, password protected. If you have a decent internet connection then you could also do it from a NAS from someone like Synology - again using an album created from photos that you have tagged
I use Zenfolio so they can just download their photos without any intervention on my part. Saves a lot of time for full wedding galleries. Thinking of moving to an "in person sales" scenario for family / dog stuff which would involve a face to face meeting and on the day purchasing of prints / wall art. I know from bitter experience that this approach doesn't sit well on STW. But I have to earn a crust 🙂
Wedding stuff, private (passworded) preview album on Nikon ImageSpace, then the rest depends what we've agreed - usually memory stick, CD/DVD, prints, occasionally a small album.
Other stuff, usually a Dropbox link or memory stick.