This thread asks on the whole how much writing down you do on your copies which will include fingering and anything else you find useful.
I used to not bother writing down a lot of the fingering as i relied on 'doing what comes naturally' when you get to it. However it feels much more proffessional and hard working to concentrate on the best fingering in the long term and keeping a record of it. I now write quite a lot on my copies.
I think it is important to write in as much fingering as possible - especially when learning a new piece or a new and very difficult piece! My teacher is always telling me off for not writing enough fingerings in! It will save you time in the long run as you can get fingerings learnt in the very early stages then - this is especially useful if you want to memorise something fairly quickly.
The danger with "doing what comes naturally" for me is that I never decide on a definite fingering and always end up doing something different each time. By doing a different fingering each time there is no stability and i will probably go wrong in a particulary difficult section.
As for accidentals/notes i'm forever writing in #s and bs here and there, i don't think there is really anything wrong with it if it helps you!
I once looked at a Ligeti Etudes score belonging to a concert pianist who performed them in a kind of performance/composition seminar type thing last year at my Uni. He had written tons of notes and accidentals all over the place! - But from how the Ligeti Etudes sounded i'm not surprised!
Some particular etudes sounded so difficult, harsh and dissonant they were the first pieces of music that ever made me feel physically sick - perhaps that is still art though because it made me feel
something (although i was also hungover at the time!)