Math mode ($ vs. $$)
Putting text between dollar signs will activate "math mode" where you can format equations and code in TeX. A single pair of dollar signs (e.g. $y = mx + b$) produces in-line math mode (ie able to use symbol for $\lambda$)
A pair of dollar signs (e.g. $$y = mx + b$$) will bump it to the next line and center it on the assignment page in a more prominent display, centered on the &.
ex:
Displays as:
Notice that \cr is needed at the end of all except the last line (to close the line), and the equations as a whole are bookended with $$ { } $$
Use those curly brackets! { } are your friend!
subscript: _
superscript: ^
Bold
$\bf{XXX}$
where XXX is what you want bolded
alignment: \eqaline
skips for vertical spacing:
\smallskip
\medskip
\bigskip
indentation:
\indent
for no indentions
\noindent
feel free to google what you're looking for with TeX as well
ex: square root TeX
\sqrt{expression}
Here's a handy TeX Reference Card with common needs!