Step 1- Determine what will fit your car.
Most CD receivers will fit in your car with the help of a dash kit. These kits are made to specifically fit your vehicle.

Step 2- Determine what features you'll need.
You need to know which discs you want to play. Most new CD receivers play home-recorded CD-Rs, with some of them playing MP3 files. Other features you might need are:

High Power Amplifiers- Most headunits have good built-in amps for loud sound played through factory speakers.

Pre-amp Outputs- If you want a really clean and loud sound you'll need pre-amp outputs to add on amplifiers and subwoofers, preferably 3 outputs (front, rear and subwoofer).

Satellite Radio Controls- These controls let you connect the satellite tuner box to receive and control digital broadcasts of XM or Sirius satellite radio.

Security features- There are many choices in theft-deterrence, detachable faces, stealth-type hide-away faces, and programmable security codes.

Step 3- Decide if you want to add on entertainment.
If you choose a changer-controlling receiver, you can add a CD or Mini-Disc changer for up to 12 discs. Many CD receivers have an auxiliary input, so you can plug in even more sources of entertainment: portable MP3 players, satellite radio tuner, audio outputs from a DVD player, VCR or TV tuner.