In Fellowship of the Ring, it is said in several places that Aragorn, Glorfindel, and perhaps even a few other people, were able to fight off Nazgûl; they can't fend off all nine at once, but if they only encounter a few at a time (the maximum number of Nazgûl each character can handle at once is stated, but I can't remember the numbers at the moment), they can hold their own, and even repel them. As if to prove the point, Aragorn forces several Nazgûl to flee Weathertop when he wields nothing more than a pair of torches.
Yet the Nazgûl are more or less immortal, and if you strike one with a sword, the sword is destroyed and the Nazgûl is unscathed (we'll leave special swords like Merry's aside for now).
So how does one fend off an immortal foe whom no normal blade can harm? Is it simply a matter of "all torches, all the time"?
Note: This question addresses issues related to "How powerful were the nine", but does not ask the same question. Rather, I am asking "By what means were Aragorn and Glorfindel able to do battle with the Nazgûl (that is, how do you fight against something you can't hurt)?" In fact, the answers to that question raise the very question I am asking, and do not answer it in any way.
It is worth mentioning that the first few people (including Sam's elderly hobbit father, Farmer Maggot, and either Butterbur or one of his hobbit employees) who encounter an individual Nazgûl in LotR manage to get rid of it by essentially slamming a door in its face and shouting "Beat it, jerk!" Nazgûl are far less impressive in the books than they are in the movies,to say the least. I imagine that if you reacted to a movie-Nazgûl by saying "SCRAM!" and slamming the door, you'd earn yourself a broken door, a number of stab wounds, and a funeral held in your honor.