1. You can define your own macro via the \def command anywhere in your document. For example

   \def\lc{\left\lceil}   
   \def\rc{\right\rceil}
   

   and then just write \lc x \rc.

2. Or you use the \providecommand in the preamble, e.g.

   \providecommand{\myceil}[1]{\left \lceil #1 \right \rceil }
   

   to simply use \myceil{x} in your document.

3. Use an editor, like vim, that allows for defining shortcuts for quick and efficient editing.
4. And, finally, don't forget about readability of your tex document. Check out this thread for some instructive comments on how to write efficient and readable tex math docs.

A LaTeX-y way to handle this issue would be to define a macro called, say, \floor, using the \DeclarePairedDelimiter device of the mathtools package. With such a setup, you can pass an optional explicit sizing instruction -- \Big and \bigg in the example code below -- or you can use the "starred" version of the macro -- \floor* -- to autosize the left and right hand brackets. Both possibilities are pursued in the following code.

\documentclass{article}
\usepackage{mathtools} % for "\DeclarePairedDelimiter" macro
\DeclarePairedDelimiter{\floor}{\lfloor}{\rfloor}
\begin{document}
\[
\floor[\Big]{\frac{1}{2}}
\qquad
\floor[\bigg]{\frac{1}{2}}
\qquad
\floor*{\frac{1}{2}}  % autosize vertical dim. of brackets
\]
\end{document}

Here is a simple xparse implementation of \ceil, similar to that provided by mathtools' \DeclarePairedDelimiter:

\documentclass{article}
\usepackage{xparse}% http://ctan.org/pkg/xparse
\NewDocumentCommand{\ceil}{s O{} m}{%
  \IfBooleanTF{#1} % starred
    {\left\lceil#3\right\rceil} % \ceil*[..]{..}
    {#2\lceil#3#2\rceil} % \ceil[..]{..}
}
\begin{document}
\[\ceil[\big]{x} \quad \ceil[\Big]{x} \quad \ceil[\bigg]{x} \quad \ceil[\Bigg]{x} \quad \ceil*[\big]{\frac{1}{2}}\]
\end{document}

The optional argument is ignored in the starred version of \ceil*[..]{..}.