Acquire a turntable with a good needle. This is essential.
Prepare your signal flow by attaching your turntable's phono RCA jacks to phono input of a DJ mixer or home audio amp (make sure the ground wire of the turntable is also attached to the ground of the mixer or home stereo amp to minimize buzz). Switch your monitor channel to "Phono."
Connect your DJ mixer or home audio amp's RCA line (or speaker) outputs to your recording device's line inputs (use a 1/8-inch mini-jack adapter if necessary).
Plug in your headphones or speakers to monitor the sound from your recording device. Launch your audio editing software (such as Garage Band) adjusting audio preferences to "Line In" for input and play your LP to test.
Make sure you are getting a good signal that is not too "hot" (too loud) or too low. Check the quality of your cables or equipment.
Adjust levels if necessary. Once you have a good signal, move to the next step.
Press "Record" on your audio editing software and begin playing your LP.
As soon as one side is done, stop your audio editing software in between flips to ensure saving your audio file and not recording more than you need.
Repeat the recording process for the other side.
When the songs you wish to archive are done recording, save your audio file project.
Edit the gaps by "truncating" or trimming off the silence between songs to minimize duration (and file size).
Export the separate songs as AIFF (Mac) or WAV (PC), 44.1kHz, 16 bit for best CD quality (128kbps or higher AAF or MP3 for archiving), titling them appropriately into a folder you create on your Desktop (or external drive for space). Garage Band's export function is located under the "Share" drop-down menu.
Test the audio file by playing it back with another audio software such as Quicktime, iTunes or Windows Media Player.
If the music sounds good, launch iTunes or Windows Media Player and import the folder to add ID3 tags such as "Title," "Artist," "Album," "Year" and so on.
Take a blank CD and insert it into your connected CD burner. For preservation purposes, choose a slower CD burn speed (2x).
After the burn process is done, take your CD and play it in another CD player (car or home stereo) to make sure it plays properly and sounds good.