Mistakes made when cutting the hair or shaving the head

What are the mistakes that some people make when shaving their heads
or cutting their hair?.
Praise be to Allaah.
Among the mistakes thatare made when cutting the hair or shaving the
head are the following:
-1-
Some people shave part of the head completely with a razor, and leave
the rest. I have seen that with my own eyes. I saw a man doing saa'i
between al-Safa and al-Marwah, and he had shaved half of his head
completely and left the rest of his hair. I grabbed him and said
tohim, "Why did you do that?" He said, "I did it because I want to do
'Umrah twice, so I shaved half for the first 'Umrah and left half for
this 'Umrah." This is ignorance and misguidance that none of the
scholars ever suggested.
-2-
Some people, when theywant to exit ihraam of 'Umrah, cut a few hairs
on their head, on one side only. This is contraryto the apparent
meaning of the verse in which Allaah says (interpretation of the
meaning):
"…(some) having your heads shaved, and (some) having your headhair cut short…"
[al-Fath 48:27]
The shortening of the hair should have an obvious effect on the head.
It is known that cutting one or two or three hairs does not have any
effect and it is not apparent that the pilgrim who has done 'Umrah has
in fact shortened his hair. So heis going against the apparent meaning
of the verse.
The remedy for these two mistakes is for the one who wants to shave
his head to shave all of it, and to shorten the hair all over the head
if he wants to cut it, and not to cut just one or two hairs.
-3-
There are some people who, when they have finished saa'i, if they
cannot find anyone to shave their heads or cut their hair, they go
back to their houses and exit ihraam, and put on regular clothes, then
they shave their heads or cut their hair after that. This is a serious
mistake, because a person cannot exit ihraam without shaving his head
or cutting his hair, as the Prophet (peace and blessings of Allaah be
upon him) said, when during the Farewell Pilgrimage he commanded those
of his companions who had not brought a hadiy (sacrificial animal) to
make it 'Umrah, and he said, "Let him cut his hair then exit ihraam."
Narrated by al-Bukhaari,1691; Muslim, 1229. This indicates that one
cannot exit ihraam until after cutting the hair.
Based on this, if a pilgrim finishes saa'i andcannot find someone to
cut his hair, he should remain in ihraam until he shaves his head or
cuts his hair; it is not permissible for him to exit ihraam before
that. If we assume that a person did that out of ignorance and exited
ihraam before shaving or cutting his hair, thinking that it was
permissible to do so, there is no blame on himbecause of his
ignorance, but when he finds out about that he should take off his
regular clothes and put on his ihraam garments, because it is not
permissible to continue exiting ihraam when he knows that it is not
permissible. Then when he has shaved his head or cut his hair, he may
exit ihraam."
From Daleel al-Akhta' allati yaqa' fiha al-Haaj wa'l-Mu'tamir
(Mistakes made by pilgrims performing Hajj and 'Umrah)