1. Vary your oscillator waveforms!
Instead of using 2 saw waves or 2 square waves detuned against each other, why not mix a saw wave and a square wave together, or even get creative using noise colours and the oft-ignored sine and triangle waves – mixing waveforms is the starting point to creative synthesizer patches.
2. Understand the ‘Decay’ and ‘Sustain’ elements of envelopes
Remember that the decay is how long the sound lasts at full volume, and the sustain is the volume at which the sound plays after the decay stage - but before the release. These two stages are essential to accurate acoustic sound emulation, and add life and dynamics to any patch.
3. Use envelopes for modulations besides the usual amplification and filter sections
If you’ve got a spare envelope (or on some synths, at least part of one) why not use it to good effect by modulating the oscillator pitch (sounds very D-50 like), PWM functions (good for percussive effects!), oscillator sync effects or ring modulation, or even the level of SFX used. The complexity of modulations performed by a dedicated envelope is far more than that of a bog-standard LFO, and can really add something extra to the start of a sound.
4. Use LFOs
Create performance effects using LFOs. Use the modulation wheel and keyboard velocity/after touch features to alter the sound while playing it. You can create a vibrato effect by setting an LFO to gently alter the oscillator pitch, a wah-wah effect by doing the same thing to the filter frequency, and a tremolo effect by altering the volume (or pan) setting.
5. Use different oscillator pitch tunings
Ever heard what it sounds like when you set one oscillator 5 semitones above the other? Instant funky harmonics! Try doing it with 7ths and 9ths and even 11ths – it creates a jazzy chord feeling. For even more complex oscillator tunings, try using the chord memory function if your synthesizer has one.