Open your Music Production Software such as Garageband, Pro Tools, Logic or Cakewalk.
Open up your existing recording session or import your recorded tracks into a new project.
Open the Mix (or Mixer/Mixing window). Here you will be able to examine the output of each track closely and directly add effects and plug-ins to each sound.
Play your composition back as it is so far. Listen closely to the levels of each instrument and think about which of these are too loud or quiet. Do any of these parts jump out uncomfortably in certain sections and are there any qualities that you'd like to remove (for example, high or low pitch rumbles)?
Examine each instrument and adjust the mix so all instruments site well together sonically. Use the mix window to reduce or increase the volume of each track or if more suitable, change the dynamics of a recording at a certain point through volume automation. Automation is the act of setting a control path instructing the software to add/reduce volume or other effects at certain points. It's useful for adding crescendos/diminuendos or for fading in or out completely.
Add compression. If you can hear that one of your recorded instruments is at the right volume level throughout except in one particular section (where it is too soft or loud) try using compression. This technique works to control the dynamic range of a track by compressing the loudest sections, therefore reducing the distance between the quietest and loudest parts. Your production software should provide you with a simple compressor plug-in to put compression into action.
Add EQ (equalization). Use this technique if you hear unusual frequencies or uncomfortable pitches/harmonics coming from a particular recording. Again your production software should provide you with a basic EQ plug-in which allows you to sweep through the frequencies being played and reduce or boost the volume of each sound.
Utilise other plug-ins. The production software you have will dictate the plug-ins and effects you have at your disposal. For inexperienced mixers, mixing music files is about playing around with effects and listening carefully to achieve the results you desire. Effects that are commonly used in a mix may include: reverb, auto-tune, delay and amp-modelling. However, there are potentially hundreds from which to choose.
Spend time "comping." If you really want to guarantee a perfect mix, take the time to use the technique of comping. This is where you sift through your recording takes and compile the best bits into one perfect track. You can do this by simply cutting and slicing your tracks or using tools, such as "Flextime" in Logic's software. This allows you to pull or squish sound waves to alter timing.