Connect your headphones to your computer. For best results, use a high-quality pair of monitor headphones. For basic recording efforts, though, any pair of working headphones will suffice.
Open GarageBand. If adding vocals to an already existing project, open the project by clicking File > Open on the menu bar and selecting the file. If adding vocals by themselves, create a new project File > New and choose a tempo (speed) on the project setup window. This will tell the metronome how quickly to tick while you sing. The average song speed is 120 beats per minute. Choose a faster tempo for fast songs or a slower tempo for ballads.
Create an audio track for your vocal recording by clicking Track > New Track on the menu bar. Select "Real Instrument Track" on the pop-up menu and click "Create." Your vocal track will then appear on your project window, directly beneath the other tracks, appearing as a long horizontal bar. This is the space on which you will record your vocals. Click the track title once in the left column to highlight the track.
Put your headphones on. In order to best keep track of your pitch, place a headphone over just one ear, while leaving the other ear uncovered. To avoid unwanted noise feedback, click the "Track Info" button on the right side of the screen (indicated by a letter "i") and click the "Monitor" button. Set the monitor to "Off."
Connect a microphone to your PC. You can purchase special USB-enabled microphone cables to connect a vocal microphone, or use your computer's internal or external microphone. Note that using a PC microphone will result in diminished audio quality. If connecting a microphone through a USB port, open your preferences panel on the menu bar, GarageBand > Preferences, click the "Audio/MIDI" tab and select your microphone on the "Audio Input" sub-menu.
Place the cursor at the very beginning of the time line by clicking "Return" on your keyboard, and click "Record" to begin the recording process. The "Record" button looks like a red dot and appears directly below the track viewer.
Set up your track for recording. On the "Track Info" menu on the right side of your project window, click the "Vocals" heading in the first column. When the list of vocal settings appears, select an appropriate filter. For spoken word recordings, try selecting "Male Speech" or "Female Speech," depending on your gender. For rock music vocals, try "Rock Vocals," "Epic Diva," "Male Basic" or "Female Basic." For pop, try "Pop Vocals," "Ambient Vocals" or "Dance Vocals." On the horizontal "Recording Level" slider (near the bottom of the column), place the indicator approximately in the center.
Sing or speak (depending on the type of project) in time with the pre-recorded audio as it plays through your headphones, or in time with the metronome ticks if you did not previously record audio. If you do not hear your metronome, select it by clicking Control > Metronome on your menu bar. When you finish recording, press the space bar on your keyboard to end the session.
Add individual effects by clicking the "Details" arrow at the bottom of the "Track Info" window and selecting the parameters you prefer. For example, if you want to add reverb or echo to your vocals, check the "Echo" or "Reverb" box and then drag the slider until you have the desired amount of effects. Check the "Compressor" box to add compression, which evens out the high and low peaks for a smoother, more natural quality. Click the four blank menus to add effects like "Bass Reduction," "Speech Enhancer" and "Tremolo."