If you have walls open (such as in an unfinished house), implement Cat-6 cables and wire your home with ethernet before it gets logistically difficult to do so. Wired is always faster than Wireless from the same source.
If you are looking to lengthen the range of your WiFi using an external antenna that can aim in a particular spot, check out RadioLabs.com (Leo's favorite source for WiFi antenna solutions). This can solve issues that Mesh Wifi would not, so for large home areas try a product from RadioLabs. Make sure to include the "S" at the end or else you'll end up at a different podcast website!
Joe had an older Mac that would allow him to send a fax through OS X, but his new computer won't do that in Mountain Lion. Leo says that was abandoned in the new version of OS X, so he can't do that function anymore with that old fax/modem. Joe needs a voice modem for faxing that's compatible with Mountain Lion. It'll likely need to be external. Leo prefers to use an online fax service, like eFax or MyFax.
If you've noticed your internet connection speed slow down to a crawl often, then there are things you can do to diagnose and fix the problem:
John keeps getting errors when trying to dial up to Net Zero's service. It could easily be that the computer he's using doesn't have a modem. He says that he does have a modem because he has what appears to be a phone plug on the back of the computer. Leo says that can easily be confused with an ethernet port, though. The next place to look is Device Manager in Windows to see if there's a modem listed there. If not, then he most likely doesn't have one. He could buy a modem if he can find a place that still sells them, but Leo doesn't think this is the best way to get on the net anyway.