Not wishing to argue, but I have never seen any evidence that your location within a system has any bearing on USS spawn rate, with the possible exception of being close enough to an object to be within its sphere of influence (it is mentioned in your targeting info box, or possibly the blue marker on your Navigation tab) - Deep Space is Deep Space, and being a games designer myself, I am pretty good at spotting "useful" code (and therefore likely to be there) and "faff" code (too time consuming to be worthwhile including). I would highly doubt that your orientation to the orbital plane or anything similarly arbitrary to anything but the pattern recognition part of the human consciousness would be coded.
Empty Systems (those without Nav Points) do spawn less USS than others - I think that is a well known fact
USSs are distributed in time, not in space, so travelling about does not help (except releave boredom). If you want to find USS - Engines to 0% (still travel at 30 or so somethings) is by far the quickest way to churn through them. They will appear pretty much in front of you and be immediately available to target and exit FSD, so there is 0 travel time. This easiest to monitor in your Navigation tab as others have said.
When doing a "fetch X from Y mission", despite the mission brief, it does not matter where you collect X from. If you are in Y, the random USS generator will be weighted in favour of your mission objectives, but if it is an empty system, you may well be better off hunting elsewhere with more USS but a lower chance of each one being the sort you are after.
