How Did the House Ghosts End Up at Hogwarts?

Question

In Tales of Beedle the Bard, Sir Nicholas (Nearly Headless Nick) is described as having been a wizard at the royal court before he was executed. His ghost then went on to Gryffindor Tower at Hogwarts.

It is true, of course, that genuine witches and wizards were reasonably adept at escaping the stake, block and noose [...] However, a number of deaths did occur: Sir Nicholas de Mimsy-Porpington (a wizard at the royal court in his lifetime, and in his death-time, ghost of Gryffindor Tower) was stripped of his wand before being locked in a dungeon, and was unable to magic himself out of his execution [...]

_{Tales of Beedle the Bard - page 13 - Bloomsbury - The Wizard and the Hopping Pot}

How did the house ghosts end up at Hogwarts?

Nearly Headless Nick is referenced above.

The Bloody Baron (Slytherin) and Helena Ravenclaw both died in Albania, when the Bloody Baron killed Helena Ravenclaw and then himself. If they both died in Albania, how did they end up haunting Hogwarts? Albania and Hogwarts were quite a distance from each other.

Is any information available about the Fat Friar (Hufflepuff)? How did the Friar die and end up at Hogwarts?

Another way of asking this question is If the ghosts of the Hogwarts Houses were killed or died elsewhere, how did they end up at Hogwarts in their afterlife? Shouldn't they have haunted the place where they had died?

★ _{I'm looking for an answer based in canon (the three Harry Potter novels, the three supplementary books, J.K. Rowling interviews, and Pottermore) and do not prefer an answer from the HP Wikia or the Wikipedia. However, if ghost lore that is relevant to this question comes from a reliable, but non-canon, source, I will gladly consider it.}

Answer 1

A ghost haunts the place that has meaning to them.

Ravenclaw's daughter haunted where her mother lived. Bloody Baron was like a typical lovesick teenager and tagged along.

We don't have canon info of what attracted Nearly Headless Nick to Hogwarts, but it could be because it was the only place where he could freely socialize (and he's painted by JKR as a rather social fellow) - the Headless Hunt wouldn't have him, and possibly other ghosts would shun him as well since he's almost headless.

Answer 2

According to J.K. Rowling on Pottermore and from Deathly Hallows

Nearly-Headless Nick (Gryffindor):

Gryffindor house is home to Nearly Headless Nick, who in life was Sir Nicholas de Mimsy-Porpington. Something of a snob, and a less accomplished wizard than he believed, Sir Nicholas lounged around the court of Henry VII in life, until his foolish attempt to beautify a lady-in-waiting by magic caused the unfortunate woman to sprout tusks. Sir Nicholas was stripped of his wand and inexpertly executed, leaving his head hanging off by a single flap of skin and sinew. He retains a feeling of inadequacy with regard to truly headless ghosts.
_{Hogwarts Ghosts}

The Fat Friar (Hufflepuff)

Hufflepuff house is haunted by the Fat Friar, who was executed because senior churchmen grew suspicious of his ability to cure the pox merely by poking peasants with a stick, and his ill-advised habit of pulling rabbits out of the communion cup. Though a genial character in general, the Fat Friar still resents the fact that he was never made a cardinal.
_{Hogwarts Ghosts}

The Grey Lady (Ravenclaw):

‘He tracked me to the forest [in Albania] where I was hiding. When I refused to return with him, he became violent. The Baron was always a hot-tempered man. Furious at my refusal, jealous of my freedom, he stabbed me.’
‘The Baron? You mean –?’
‘The Bloody Baron, yes,’ said the Grey Lady, and she lifted aside the cloak she wore to reveal a single dark wound in her white chest.
_{Deathly Hallows - Chapter 31: The Battle of Hogwarts}

The Bloody Baron (Slytherin):

‘When he saw what he had done, he was overcome with remorse. He took the weapon that had claimed my life, and used it to kill himself. All these centuries later, he wears his chains as an act of penitence … as he should,’ she added bitterly.
_{Deathly Hallows - Chapter 31: The Battle of Hogwarts}

And why they end up at Hogwarts:

[Hogwarts] is a congenial place for ghosts, because the living inhabitants treat their dead friends with tolerance and even affection, no matter how many times they have heard the same old reminiscences.
_{Hogwarts Ghosts}

This, in addition to the fact that (at least) three of them attended Hogwarts, it is natural that they gravitated back after they died.