Seems like nobody's mentioned it yet, so I will: A regular tape player won't get you the results you're likely looking for. Cassettes have a total of 4 available tracks - this is done to acheive sterephonic sound, meaning 2 channels per side of tape (Left & Right). A typical home cassette player can only read two channels at a time, whereas a multitrack recording device like those old tascams read all four channels simultaneously.
In practice, this means that if you play your old demos and stuff on a regular player, you'll only hear two of the tracks you recorded, and some of them might even play backwards, depending on which track you used at the time.
So. Make sure you are using a 4 track recorder to pay back your tapes. Just use the stereo/mix out (it's usually a phono plug), and send that to the preamp of your choice. Open up your DAW, hit record, press play on the deck and walk away. Easy peasy.