There are 3 different ways for you to connect with hardware: DreamPi, VoIP, and Landline.
DreamPi is the most reliable method, but you need to have a few different things
for it to work.
VoIP isn't as reliable as DreamPi, but all you need is a VoIP adapter.
Landline is the least reliable method, but if you have a landline already you
don't have to buy anything.
Most Reliable - Hardest
Moderately Reliable - Somewhat Difficult
Least Reliable - Easiest
If you're planning on connecting with a Dreamcast, follow one of the guides above
to get your dial-up setup configured, then follow this guide:
Decent alternative to a WebTV box for Dreamcast owners