Alas the thread was not as I thought, so here is the lowdown (from my end).
A minor point, I will be primarily talking about drums because they can make the most obvious sounding changes, but pretty much everything applies to melodies and harmonies as well.
First thing to consider when trying to make stuff sound more organic is that humans along with their capacity to play instruments are not perfect.
Even the best drummer in the world won't hit every beat perfectly, some of them maybe, but not to the extent that your DAW would quantize it.
So... tip #1 is either tap/play your beats/melodies in by hand. It may be hard and you may have to redo it a few times or tweak it afterwards, but it will be well worth it, trust me.
While you can just exclusively do this as a way of making your stuff sound a bit more "real" or "live" you can also do this to achieve a specific effect.
If we take for example the most basic form of dubstep drums, kick on one and snare on three with a couple of high hats inbetween.
By the way please do try this out so you know what I mean.
If you shift the hats and the snare slightly to the right then your beats can sound quite sluggish or plodding which can be good if you are using it on a slow lazy track with a reasonably low energy.
Conversely if you move your snares and hats (and in some situations kicks) slightly to the left then you will get a sense of immediacy and your beats will appear to have more energy.
Bear in mind when I'm talking slightly I mean really tiny amounts, so it still sounds pretty much in time but has either a more stumbling or more upfront feel.
The same also applies to melodies, although I will stress if you are going to do one thing with your beats, you are probably better off doing the same with your melodies, otherwise it can sound quite jarring (obviously not a hard and fast rule but generally true).
Think about a real drummer for a second, he is realistically never going to hit a drum twice with precisely the same amount of force, and based on the force he hits it with and where he hits it, it could make many distinctly different sounds with all sorts of tonal differences. Sooo...tip #2 is to try to vary your the velocities of your notes. (Also, side note, if you can get a drumkit patch with lots of velocity layers it will make a whole bunch of difference.)
When doing this there are a number of things to consider, for example in common time (4/4) there is a stress on the first note of the bar and a slightly smaller stress on the third note of the bar, so if I was programming in a 4 hit pattern in this time signature it might go something like...
Hit one = 127 (velocity)
Hit two = 100
Hit three = 115
Hit four = 105
Other than time signatures, think about the drummer himself (were he to exist), he is either going to be left or right handed. Except for a tiny portion of drum virtuosos a drummer will almost always have a harder hit with their strongest hand, so try and replicate this.
Keeping with the subject of our imaginary drummer we get to tip #3 a drummer has two hands and two feet, meaning that unless he is from mars then he can only play at one time: a kick, a high hat pedal (obviously you could have the pedal linked to something else but that would be extremely rare) and two other drums (i.e. two tom toms). So if you have a snare, a tom tom and a ride cymbal, thats just not going to fly I'm afraid.
This also ties in with the left and right handed thing, it is going to be very difficult for a drummer to play (with one hand) something on one side of the kit very soon (like really really fast) after playing something on the other side.
Finally a bit more about melodies and more specifically sampled instruments. Choose your sounds carefully, if you are going to something slow and mournful, don't use a staccato (a short burst of drawing the bow across the strings) violin, likewise if you are going for powerful and epic, maybe dont go for the smooth sounding finger plucked guitar.
Obviously these are not hard and fast rules and the most important thing is to feel where the music wants to go and what it wants to do with itself, but give some of them a go.
Be warned however, doing this and making it sound good takes SHITLOADS of time, because you literally have to customise EVERYTHING! And still nothing really beats a human player for sounding human.
