When creating patches, the amount of control given to you by the synthesizer is virtually endless. Experimentation often leads to disappointment. What will take your sound beyond the random and make it an element in your music? Here is a checklist of sound design principles to keep in mind when you are finalizing your patches or music for greater artistic impact. This will not be useful for people messing around with their modulars, but it could be helpful for someone that does a lot of programming.
Can you group your synth voices (OSCs) into the same category? or do they conflict? Two string instruments will have a similiar waveform. We may group these sounds in our minds upon playback. However, a simultaneous synthesizer OSC and a saxophone sample OSC could be discernable from eachother. We are used to hearing them. This is contrast. A great example of unity would be a chorus. You can even achieve unity by placing the same effect over multiple sounds (like a phaser/chorus, Daft Punk effect). Frequency also contributes to unity, as oscillators tuned in a harmonious way compliment eachother.
How to achieve Unity - Similar waveshapes. Similar octave. Similar playback levels. Similar scale. Same effects over multiple sounds.
How to achieve Contrast - Dissimilar texture, waveshape, levels, different effects.
Stereo Field, Depth (Panning & Effects)
Where the sound is in relation to other sounds creates a stereo soundstage. Do you want a big sound? You might want lots of reverb and long delay. Do you want the sound to ominously disappear into the background? Maybe it doesn't need to be so loud, maybe it doesn't need all that brightness (treble EQ), or energy (mid/low eq). Stereo effects can give your sound unity and place them in relation to other sounds. When you are making a patch you might want to consider how the effects will relate to other sounds.
EQ / Balance
You may want to think about where your sound will fit in the sonic spectrum. This could be genre dependent too. You might want to turn the sound up louder than normal and EQ it to your own taste.
Voice and Texture, Color
The voice, again is mainly what type of sound you are creating and its emotional impact. It also has to do with culture and genre. Many sounds we've already heard before. Synthesizer sounds used to be novel to humans, but they no longer are. Many people have already heard them on video games and pop music. What type of waveform are you creating? How does it make you feel? A low sound may be scary, a high frequency sound, may sound more feminine or annoyingly like an insect. Texture has to do with many qualities like the recording equipment (vintage), distortion, and the frequencies captured. It could be something subtle, like noise. A smooth sound will have less frequencies (a single sine wave) a harsh textural sound will have many frequencies (a snare drum).
Time and Rhythm (Patterns)
Modern synths allow custom step sequencers, LFOs, and other time effects. Popular Dubstep uses a simply timed LFO-to cutoff filter effect. Most pad sounds have elaborate time and rhythm that effect levels, filters, and stereo field. Basically, you could use time and rhythm to affect every aspect of the sound (EQ, Depth, Unity) over time. This makes the sound dynamic and emotionally changing. Euro-trance music used long amounts of time and filter brightness to create an energetic uprising. A faster speed can create rhythm and create a sonic intensity. A random change can create chaos. Use time and rhythm to fit with your genre or vision within the sound itself. It will make creating the music easier.
Articulation and Performance
The latest keyboards feature extensive performance and dynamics. This can be as simple as assigning velocity to multiple parameters. Do you want to change something with the pitch wheel? Do you want multiple parameters to be controlled simultaneously. Allowing more control to the patch's parameters can make them more fun to play.
Hopefully you can use this checklist to finish your patches and increase the emotional impact of your patches. Maybe in the future, more synth designers will categorize the parameters by these principles.