I'm somewhat of a LaTeX noob, and this is driving me completely nuts.
When I type
\documentclass{article}
\usepackage{enumitem}
\begin{document}
Some text
\begin{itemize}[noitemsep]
\item Item 1
\item Item 2
\item Item 3
\end{itemize}
\end{document}
I don't want the space which appears in between the text "Some text" and the itemization to be there:

When I search around on Google all I see is tons of long, complicated advice on this site, StackOverflow, forums, etc. on how to not fix the problem ("parskip is evil", etc.), or tons of vague/confusing answers on what package to look at, with no actual example for me to learn from.
So while this question is already asked many times, I have never found a single concrete answer to this question.
The question couldn't be simpler: How do I "properly" get rid of this extra space?
ACCEPTED]
That space is governed by topsep. Set it to 0pt.
You can customize itemize/enumerate environments very easily using the enumitem package.

\documentclass{article}
\usepackage{enumitem}% http://ctan.org/pkg/enumitem
\begin{document}
\noindent Some text
\begin{itemize}[noitemsep]
\item Item 1
\item Item 2
\item Item 3
\end{itemize}
\bigskip\bigskip
Some text
\begin{itemize}[noitemsep,topsep=0pt]
\item Item 1
\item Item 2
\item Item 3
\end{itemize}
\end{document}
To set this globally, use
\usepackage{enumitem}
\setlist[itemize]{noitemsep, topsep=0pt}
See section 5 Global settings (p 9) of the
enumitem
documentation
[1] for more details on this and perhaps creating your own list environment that has these predefined settings.
The enumitem package now provides [nosep] to suppress the space above and below lists as well as the space between items. However, this option does not suppress the space above and below the list if you are also using the parskip package in your document.
parskip doesn't provide a nosep option. - Werner
enumitem rather than parskip? But it's not a package option anyway. - egreg
parskip? - incandescentman
\setlist{nosep, before={\parskip=0pt}} - wfsch
An alternative to this is to just use:
\usepackage{paralist}
And the compactitem environment:
\begin{compactitem}
\item This is entry number one, compact
\item This is entry number two, compact
\end{compactitem}
to see more on this, check: Compact lists with paralist.
Between an itemize environment and its preceding text, a length, \parskip, also adds to that space. Enumitem package does not control it. To completely eliminate that space without changing \parskip, you can use
\usepackage{enumitem}
...
\setlist{nosep,topsep=-\parskip}
to offset that space globally. You may also set it per-environment.
\SetEnumitemKey{noparskip}{nosep, topsep=-\parskip} - jw5801
In some cases you might need to add \nointerlineskip after an itemize environment to get rid of spacing below.
\vspace{-0.5\topsep} and \nointerlineskip before and after worked for me with beamer. Nice thing: no additional package needed. - mfg
This worked for me, add minus topsep=-8pt
\begin{itemize}[noitemsep,topsep=-8pt]
noitemsep,topsep=-8pt is appearing verbatim at each item, instead of being used to adjust the spacings. - Della
enumitem - robertspierre
topsep=-\parskip - jw5801
For people that still can't figure it out, just do the dumb-down straight-to-the-point method \vspace*{-#mm} underneath the item for example, 
itemize. You can also create your own list with these settings, if need be. - Werner\newenvironment{Itemize}{\begin{itemize}[noitemsep,topsep=0pt]}{\end{itemize}}. But I would go for Werner's solution. - hpesoj626\setlist[itemize]{noitemsep, topsep=0pt}you can also say\setlist{nosep}, which kills all vertical spacing. - Roaldbeamerclass (or something else). - Wernerenumitem. Just copying the itemize block won't work. - Thomas\usepackage{enumitem}in the preamble, so that means that I am "using the packageenumitem." - Wernertopsepandbottomsep? Or where to check them, for that matter? - Daneel Olivaw\documentclass{article}, the default font size is10pt, with the list parameters\@listiset insize10.clo. There's alsosize11.cloandsize12.cloif you load one of the default classes with either11ptor12ptoptions. - Wernernoitemsepandtopsep=0pt(which is equivalent tonosep) and the second page sets a similar list as a bunch of\paragraphs. Without investigating, I think the bottom gap is just whatever you have for itemsep, so not necessarily\baselineskip. - Werner