Yes, there are lots of variables, BUT you have to start somewhere!
Clean hands/equipment, keep the temp low, don't have it out in the open any longer than you have to etc ARE all common sense.
But without the sell/best by date you have NOTHING to go with!
Yes I have had food poisoning befor (not by home prepared food tho') and no I don't wish to repeat the experiance, but unless you have a bacteriometer (OK I just made that up
) then the best thing to go by is common sense and the sell by date.
Don't forget we regularly hang meat for long periods specifically so they will rot a bit just to improve the flavour!