I find that enabling the microphone with Alsa is very painful. Here is a detailed step by step explanation
You'll need to launch alsamixer from a console.
Use the left arrow key till you get to the Capture channel. Press the
space key you should see CAPTUR on top of the bar in red. Next
increase the channel volume with the up key.
Make sure that you you have Mic1 selected on the Mic Select
channel. Last it can be a good idea to unmute the Mic Boost channel to
amplify your microphone input.
Now that was really simple wasn't it? Yeah right...