The Best PersonThe "best" person to master your product is probably "you." You are the one who is communicating through music. You know what's important about the sound you want and what is less important. You know what you were trying to achieve in the production and where you hit or missed the mark in recording and mixing. The outside "mastering engineer" can only guess.
You may be the best person, but you may be untrained in the mastering process or have difficulty in understanding how to master your specific product. You may think it is an impossible task to learn enough to do a good job, but it doesn't have to take that long for you to "beat out" the quality of what is offered by most "mastering engineers" in the industry. You can achieve "good mastering" quality by today's standards quickly, and if you keep at it, you can eventually achieve "great mastering" quality.
How do I learn to Master?Step 1 - Study
For one thing, you do a lot of reading. Even the instruction manuals can be helpful on learning some basic techniques, but let me give you a warning about that source, which also applies to most "books" on mastering. It is very easy to be lead down the wrong path if you don't study enough different viewpoints about mastering.
An example of reading something that can take you down the wrong path includes Ozone's Mastering Guide. A lot of really good information in this publication. But, just reading the text, you could get an idea that "matching spectrums" is they way to EQ while mastering and the use heavy limiting is that way to get a loud master. Both of these techniques are really going in the wrong direction.
Then there are texts on mastering that can help you. A very good, quite in-depth, text on mastering is "Mastering Audio - The Art & Science." by Bob Katz. But, as good as any text is, it could give you ideas about what must be done in mastering that really don't fit your situation. An example of this is that you could come away with the feeling that high-quality mionitors and a room with good acoustics is essential to mastering. Where some of these things may be necessary to doing the best job in the quickest manner, they are not essential to being able to do a "good" job with mastering.
Another excellent way to get information on how to master your product is through posting by professional mastering engineers in forums. Then of course there are "mastering courses" by excellent instructors that can greatly improve your mastering technique. (Let me see if I can think of an in structor

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2. Get Some Basic Tools.
I think it is much more important to learn how to use the tools rather than to buy expensive tools. Programs like Ozone, WaveLab and SoundForge can give you good results if you know how to set the parameters and use the programs. These kinds of programs can cost less than 10% of the amount that certan programs (read "WAVES") can cost you and can even sometimes do a better job in the right hands.
I recommend to my students the purchase of Izotope's Ozone and Stienberg's WaveLabe Studio software to get started. This "package" costs less than $300 with academic discounts and about $500 without those discounts.
You'll need a computer. You optimumly should have a dedicated computer, but reality is that you probably could use a $300 desktop model if you keep it virus free, throw out all those silly programs you'll never use, and disconnect it from the web while you are mastering.
You'll need a monitor system, reasonable headphones and a $40 sound level meter so you can adjust your listening enviornment. The monitor system doesn't have to play loud, doesn't have to be expensive, but needs all of the frequencies present (read "has subwoofer"). You'll need to set this up the best way you can (see some of the tips on this forum) and use near-field monitoring if your room is not up to snuff acoustically.
3. Hire A Professional Mastering Engineer
Now hire a professional mastering engiineer to master ONE CUT. Try to find one that is both a good engineer and one who is communicative about what was done to get that one cut sounding right. You could possibly book a mastering session where you are sitting in on the mastering - it can be more expensive, but will give you good ideas about what to do because you observed the sessiion. Take your project home and, using your basic tools, try to get all the cuts up to the quality of the one done by the professional engineer. Then maybe hire a different engineer to master one more cut - take your project home and work on it. Maybe you'll need a third or even a fourth cut mastered in this manner, but with each cut you get yourself closer to being able to do it yourself.
so, to repeat myself, the best person to master your project is you - this tip was on how to do that.

bob