I often spend time just randomly messing around on synths - flipping though patches, playing some notes and chords up and down the keyboard to see if something grabs me and most importantly making notes about anything of interest so I can find it again and remember why it was interesting.
Thats a starting point often for a track too, though not nescesarily a hook or whatever (unless a guitar or piano etc part was allready laid down, etc) - other sounds will follow on from that and each have a place - layers/accents, counter melodies, rhythmic, energy, leads etc. Often I'll hear a sound in someone elses music (ie on a CD, record, video etc) that I like and may start by programming something similar even if in the end the use is different.
I do have a bunch of favourite patches on various synths and favourite fx in various plugins and fx boxes that I go back to alot and tweak quite a bit each time I use them in general categories of pads, pad-arps, bass sounds, leads, stabs, polysynths etc.
The key thing I often need to be able to do is find the right flavor of sound very quickly and thats where previous time spent siftimng thorugh patches and making good notes is really valuable.
Even without the time pressure of others waiting on you to find the right sound - there is allways the time pressure of finding the right sound before you loose the idea in your head - often thats harder
