How to hook up droid phone to play through the car stereo?

There are many ways you can achieve this, here's two. The more difficult and more expensive way to do it would be to buy a stereo head unit for your car that has an auxiliary input. Have the head unit installed or install it yourself. Then insert a 3.5mm male to 3.5mm male stereo plug into the aux input of your head unit and the headphone jack on your droid. (Note: Most newer model cars have an AUX input built in.) A second more cheaper option is to buy an fm transmitter that you plug directly into your droid headphone jack. The transmitter will then transmit the fm signal on a specific channel to your car's stereo. Although this is an easier and much cheaper option fm transmitters can be extremely flaky. If you don't have a good radio in your car already this probably wont work great for you. Option 1 will cost you at least $75 or more depending on if you have someone install the head unit. Option 2 will cost you around $30 or so depending on what brand you buy. (it's important to buy a good quality transmitter. Read reviews before you buy!)

If you car has blue tooth then just sync it up and it will play through the radio. If it doesn't you can buy connectors to do it if your radio is on a station with no reception.

If you car has blue tooth then just sync it up and it will play through the radio. If it doesn't you can buy connectors to do it if your radio is on a station with no reception.