Atonal is about the music doing something you (as a hearer) don't expect. What exactly is atonal changes with different eras and different people, but general guidelines exist.
100% tonal is bad, music like this is often boring as hell. You want to induce tension, and you usually do that with dissonance, but not too much (or just solve the dissonance to make it make sense, more on that later).
We (as in, modern western world) are very very used to major and minor scales, and hence perceive things not obeying them as discordant and random (Assuming you know what they are, if not ask).
Especially if you're doing dance-ish music, you should stick to them.
Depending on what genre you're making, you'll sometimes want to change scales. This is where all the fun begins, as there are hundreds of possible paths through scales that can sometimes be very beautiful.
In general, here are intervals ordered in "pureness" or tonality from my point of view:
Prime (same note... hur dur)
Octave
Quint (5 notes, eg A-E) / Quart (4 notes, eg E-A)
Large Terz (3 notes, eg A-C#) / Small Sixth (6 notes, eg C#-A)
Small Terz (3 notes, eg A-C) / Large Sixth (6 notes, eg C-A)
Large Second (2 notes, eg A-B) / Small Seventh (7 notes, eg B-A)
Small Second (2 notes, eg A-Bb) / Large Seventh (7 notes, eg Bb-A)
Tritonus (half an octave, between quint and quart, eg A-D#)
Maybe this helps. The same thing can be used as a rule of thumb when changing harmony, but there are a lot of other factors there that count.
To your song:
0:00 - 0:26 Not specifically atonal, but not really tonal either. Remember that the more you repeat something, the more tonal it becomes. Good for atmosphere, especially if you're aiming for something mysterious.
0:27 - 1:11 Quite tonal, nice major tone. Since you're trying to build up tension, I don't quite agree with that, reminds me a lot of this:
http://www.youtube.com/watch?v=3Wp2QGKl1uU
1:11 - 1:13 Big wtf, standard dubstep surprise, not perfect (lacking power), but not disturbing either.
1:13 - 1:15 This is far too dissonant. It distracts (me) completely from the song and also breaks any groove, just makes me want to mute it. Avoid tritonus'es in dubstep
.
1:15 - 1:38 The rest of the drop is sort of dissonant and chaotic, although not as much as the above part.
And then it repeats.
TL;DR: Use minor scales and sometimes major for arpeggios, avoid using half-step intervals or tritonus'es, and try sticking to a few scales (in dubstep, you can even get away with one).
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