You can use \newenvironment to make a step by step environment, steps:
\documentclass{article}
\usepackage{enumitem}
\newenvironment{steps}[1]{\begin{enumerate}[label=#1 \arabic*]}{\end{enumerate}}
\makeatletter% http://tex.stackexchange.com/questions/29517/forcing-new-line-after-item-number-in-enumerate-environment/29518#29518
\def\step{%
\@ifnextchar[ \@step{\@noitemargtrue\@step[\@itemlabel]}}
\def\@step[#1]{\item[#1]\mbox{}\\\hspace*{\dimexpr-\labelwidth-\labelsep}}
\makeatother
\begin{document}
\begin{steps}{Action}
\step Bla, bla, bla...
\step Bla, bla, bla...
\step Bla, bla, bla...
\end{steps}
\begin{steps}{Thing}
\step Bla, bla, bla...
\step Bla, bla, bla...
\step Bla, bla, bla...
\end{steps}
\end{document}

To further refine this approach you can declare the environment using the LaTeX3 function \DeclareDocumentEnvironment. It lets you specify optional arguments and set defaults for them. The following declares a new environment, steps, which if it's not given any argument defaults to the label "Steps":
\documentclass{article}
\usepackage{enumitem}
\usepackage{xparse}
\DeclareDocumentEnvironment{steps}%
{O{Step}}% If no argument is given the label defaults to 'Step'
{\begin{enumerate}[label=#1 \arabic*]}%
{\end{enumerate}}
\makeatletter% http://tex.stackexchange.com/questions/29517/forcing-new-line-after-item-number-in-enumerate-environment/29518#29518
\def\step{%
\@ifnextchar[ \@step{\@noitemargtrue\@step[\@itemlabel]}}
\def\@step[#1]{\item[#1]\mbox{}\\\hspace*{\dimexpr-\labelwidth-\labelsep}}
\makeatother
\begin{document}
\begin{steps}
\step Bla, bla, bla...
\step Bla, bla, bla...
\step Bla, bla, bla...
\end{steps}
\begin{steps}[Action]
\step Bla, bla, bla...
\step Bla, bla, bla...
\step Bla, bla, bla...
\end{steps}
\begin{steps}[Thing]
\step Bla, bla, bla...
\step Bla, bla, bla...
\step Bla, bla, bla...
\end{steps}
\end{document}

stepsis given no argument. – N.N. Oct 26 '11 at 17:51