Where to put new LaTeX packages

The mcode package, for instance, is in:
~/Library/texmf/tex/latex/mcode
Now why doesn't the Mac OS search function find this file?

Latex - more commands

I've been doing 3 problem sets/week in LaTeX for the last several weeks; here are some more tips to follow up on my previous post:

Making your own functions:
\newcommand{\norm}[1]{\left\Vert #1 \right\Vert}
\DeclareMathOperator*{\argmin}{arg\,min}
The * puts the subscript below the operator. To stack subscripts:
\min_{\substack{ X>0 \\ Z \\ W=W^* }}

Different vector formats
Underline, with the line crossing descenders (as in gjpqy):
\usepackage{soul}
\setuldepth{abcdef} % sets ul depth based on letters w/o descenders
\newcommand{\vecu}[1]{\text{\ul{$#1$}}\xspace}

Bold:

\newcommand{\vecb}[1]{\ensuremath{\boldsymbol{#1}}\xspace}

And one more layer of shortcut/indirection (overwrites the caron diacritic)

\renewcommand{\v}[1]{\vect{#1}}

Shortcuts that I've found useful:
\newcommand{\reals}{\ensuremath{\mathbb{R}}\xspace}
\def \ba#1\ea{\begin{align*}#1\end{align*}}
\newcommand{\ii}{^{-1}}
\newcommand{\intii}{\int_{-\infty}^{\infty}}

Matrix formatting
check out these posts from Stefan Kottwitz's excellent TeXblog

A cool trick to turn + - = into alignment marks (e.g. for systems of linear equations)
http://tex.stackexchange.com/questions/6965/multicol-layout-for-systems-of-linear-equations

Cool stuff with figures
http://en.wikibooks.org/wiki/LaTeX/Floats,_Figures_and_Captions

MATLAB code
Get the mcode package, which configures the listings package use with MATLAB. The demo is pretty self-explanatory, and the package works great!

Miscellaneous:

Accent marks:
http://en.wikibooks.org/wiki/LaTeX/Accents

Found this while researching this post and learned a bunch of new things:
http://www.math.uiuc.edu/~hildebr/tex/basics.html
For example, use \eqref to put parentheses around the equation number.

To reduce vertical spacing around section headings: \usepackage[compact]{titlesec}

Cursive lowercase l, as in l₂: \ell

LaTeX: getting back in the saddle

After spending more than a year away from LaTeX, I have forgotten so much. Here are the things I've had to look up so far:

Setting up LaTeX

I'm using a Mac now and TeXShop. Fortunately it comes with a template, which I've modified slightly (to use the "article" document class). I also installed cocoAspell, which is a dictionary that will filter out the LaTeX keywords. After installation, you have to go to its section in System Preferences to enable the dictionaries and turn on the LaTeX filter. You could go to either System Preferences -> Language & Text or TexShop's Edit->Show Spelling and Grammar (or both) to set it to use the Aspell dictionary.

LaTeX commands

To change the section and subsection numbering style:
\def\thesection {\arabic{section}.}
\def\thesubsection {(\thesection\alph{subsection})}

Set of all reals:
\usepackage{amssymb}
\mathbb{R}

Indicator function:
\usepackage{bbm}
\mathbbm{1}

Lots of symbols:
http://www.artofproblemsolving.com/Wiki/index.php/LaTeX:Symbols

Aligned equations:
\usepackage{amsmath}
\begin{align*}
g^{-1}(\xi) &= \{x \in \mathbb{R}: g(x) = \xi\} \\
h^{-1}(\psi) &= \{y \in \mathbb{R}: h(y) = \psi\}
\end{align*}
If you're trying to align a single equation in multiple places. The parameter is # of columns, which is (# of & signs + 1)/2. Every other & is for alignment, the other ones specify where to add the whitespace.
\begin{alignat*}{2}
f &= ax + b && \ge 0 \\
h &= cx && = 0 
\end{alignat*}

Defining a piecewise function, with the big curly bracket:
f_{Z|X}(z,x) = f_{Y}(z-x) = \begin{cases}
\frac{\mu^{z-x}}{(z-x)!} e^{-\mu} & z-x \ge 0 \\
0 & z-x < 0
\end{cases}

Keeping fractions big:
\frac{\displaystyle ...}{\displaystyle ...}

Particular spacing:
\int x\,dt
i.e.\ in other words

Command shortcuts:
\newcommand{\norm}[1]{\lVert#1\rVert}
\newcommand{\reals}{\ensuremath{\mathbb{R}}}
\def \ba#1\ea {\begin{align*}#1\end{align*}}

Tables:
http://en.wikibooks.org/wiki/LaTeX/Tables

Keeping functions together:
\relpenalty and \binoppenalty
http://www.guyrutenberg.com/2006/12/10/prevent-line-breaking-inline-formula-in-texlatex/

LaTeX things I keep forgetting

Itemize and enumerate spacing 

To change the spacing of an itemize environment (or of anything, really, it's just most annoying with itemize):
\setlength{\itemsep}{2pt}
\setlength{\parskip}{0pt}

If you're going to do a lot, then you can define a new environment
\newenvironment{name}
{
   \begin{enumerate}
   \setlength ...
}
{
   \end{enumerate}
}

Graphics
To crop:
[trim=95 25 95 15,clip]
It's left, bottom, right, top

To define a bounding box:
[bb=0 0 719 570]
It's x,y,width,height

Header

\documentclass[12pt,letterpaper]{article}
%\parindent0em
\usepackage{graphicx}
%\usepackage{subfigure}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{float}
\usepackage{lscape}
%\usepackage{mcode}
\addtolength{\oddsidemargin}{-.75in}
\addtolength{\evensidemargin}{-.75in}
\addtolength{\textwidth}{1.5in}
\addtolength{\topmargin}{-.25in}
\addtolength{\textheight}{1.25in}

Note that the length adjustments are based on my LaTeX=>ps always outputting in A4 paper rather than letter...

Hmm...had an issue this time with LaTeX=>ps turning my .jpg into black & white...odd...
But the rest of these tips should work!