how is Harry going to find the horcruxes?

I think that Dumbledore and Fawkes will be there to help Harry. Hagrid, Lupin, Sirius, and even Snape can help him find the other Horcruxes. ROn and Hermione will support him as well as the rest of Dumbledore's Army... Harry can also seek help from Dobby and Hedwig... Harry has so many options from whom to ask help from. He's not alone.

perhaps another character will be introduced that will guide and helpHarry in finding all the remaining horcruxes and ultimately destroy the dark lord, maybe the one with the initials RAB, or maybe Harry will just rely on the help of the remaining members of the order. It could also be that Dumbledore left some diary or journal (like the one Tom Riddle made) that will give Harry clues and ideas on how to find all the horcruxes... this are all just my speculations though, and i'm eagerly awaiting the last book to find out how near or far off the mark my guesses are. ;)

About the pensive i am still apprehensive but to my guess i suppose the intution about voldemort's intentions which he developed in "Order of the Phoenix" would play a great role and Voldemort would be checking all his horcruxes and that would lead harry to them.