Funny, I have been transferring about 50 tapes over this last month into digital and I am doing one right now as I write this....
Tapes from the 70's & 80's will begin or have already begun to deteriorate and will need to be transferred if you still want them for the future.
If people who have old tapes do not do this now, they will lose their precious memories. If anyone has tapes from the 70's through the 80's, they need to do this now, or goodbye tapes.
When I first started doing this, I saw that some of the tapes have already or were in the process of loosing it's audio and going fast, and is why I have been hurrying to get this done over the month. Of course it depends on how they are stored, but generally, age is "killing them".
Even some old CD's that were originally said to "Last for 100 years" are starting to go as well...
I have been using Audacity and it is great for this task. Yes, Garageband can do it, and any other Audio Recording software, but Audacity seems to be the easiest with less hassle for this task.
You will need to purchase a Cassette player that has a USB connection for the easiest transfer, but you can use a regular player with an 1/4" audio chord out of the headphone port if needed. I purchased a Cassette player with an USB out on Amazon for about $25-30 if needed.
Easiest way to do it is install Audacity plug in your cassette player, hit the play button on your cassette player and click the record button on the software and you are good to go.
Once it has recorded, go to the effects section found in the tool bar and scroll down to "Normalize" and hit "ok". This will bring up the levels to a good listening level. If you want to get fancy, you can play with the effects and use them to get some of the noise out, speed up a little some of the slowness in playing speed that happens sometimes to the tape as it gets older, and/or EQ it to sound better.
To edit out things from the audio, just highlight what you want to get rid of and hit delete and you can edit out things quickly.
Then go to "Edit" on the task bar and select "select all audio" and export it out. It will export it out as a large .wav file, but you can add/download a plugin from AudioCity's site I think (or search internet) for a plugin for .mp3 to use to export out as an .mp3. I use another audio converter for this task instead of a plugin.
That is the basics and should work for general use. Have fun!