I guess in that case, I don't do much noodling at all. I seldom just pick up my ukelele and play whatever, then put it down. I do often times think, "I wonder what that would sound like", and then I run up and see.
But where do you take it? Do you just figure out what your thought was and leave it at that, or do you then try to find some useful applications for it?
Case in point: I was listening to the Brandi Carlile album, Bear Creek, the other day and thought "Hey, I like the tune 'Keep Your Heart Young.' I'll bet it's in G, with a couple of chord changes." So when I got home, I grabbed my ukulele and played a couple different chords and sure enough, it's in G. Played along with the recording twice and got the gist of it. Put the uke down and went about my business.
For me, that was noodling.
A couple of days later, I sat down and worked on the chords more intently; what voice leading would be good for the verse, where it could fit into the chorus, any chords that might be odd (like the Gmaj/B that was in the chorus), etc., and then pulled out the metronome and played along with that to make sure my chords were "playing well" with my strumming patterns.
For me, that was practicing.
Where does creativity fit in?
Honestly, both in practicing and noodling.
I write a lot of solo bass compositions, many of which started out as just noodling while I was killing some time. HOWEVER, the countless hours of practicing technique, studying theory, running scales all provided the foundation so when I was "noodling," I could easily figure out what it was that sparked my interest, and replicate it easily. And then, arrange it in such a way to give it life as a song. Without that solid foundation, it would be much harder to take an idea from concept to completion. It would be luck.