Q:

How do I type a single bracket?

How do you produce a single bracket in LaTeX? I just want to insert a " [ " without closing the bracket. Is there a way to do this?

A:

If you wish to have have a scaleable bracket you should use the following:
\[ % Enter math mode
  \left[ your_formula_goes_here\right]
\] 

If you want to keep it only on one side, use:
\[ % Enter math mode
  \left[ your_formula_goes_here\right.
\] 

or
\[ % Enter math mode
  \left. your_formula_goes_here\right]
\] 

depending on the side.
The important part is to always close with \right<**> whatever you opened with \left<*>. Note, as @Werner mentioned, that * and ** could be different as in \(\left] x^{x^{x^x}}\right\}\).

