[Tex/LaTex] How to align the list (enumerate) with the start of the paragraph

Question

I am having an issue aligning the left side of my list with the left side of my paragraph. Here is my current code:

Code:

\documentclass[draft, 12pt]{article}
\usepackage{fullpage}
\usepackage{enumitem}
\parindent = 0pt

\begin{document}

This is a random and long sentence that apparently takes up two lines just so that I 
can see what happens with alignment and indentation. Note my \texttt{parindent = 0pt}.

\begin{enumerate}
    \item This is list one first item.
\end{enumerate}

\begin{enumerate}[leftmargin = 0pt]
    \item This is list two first item.
\end{enumerate}

\end{document}

Visual representation:

      This is a random and long sentence that apparently takes up two lines just so that I can see
      what happens with alignment and indentation. Note my parindent = 0pt.

           1.  This is list one first item.

1.  This is list two first item.

Answer 1

The solution depends on how many items you are expecting in the list. If the number of items is 9 or less than use:

labelindent=0pt,labelwidth=0.75em,leftmargin=!

but for 10 thru 99 you should use a larger labelwidth=1.25em

Notes:

• The showframe package was used just to show the page margins. It is not needed in your actual use case.
• Manually setting \parskip is considered a "deadly sin" as per Too much whitespace before lists when changing the \parskip length. Use the parskip package instead.
• A good reference for the horizontal spacing parameters is can someone please explain the enumitem horizontal spacing parameters?.

Code:

\documentclass[draft, 12pt]{article}
\usepackage{fullpage,showframe}
\usepackage{enumitem}
%\parindent = 0pt
\usepackage[parfill]{parskip}% Use this instead of \parindent = 0pt

\begin{document}

This is a random and long sentence that apparently takes up two lines just so that I 
can see what happens with alignment and indentation. Previously \verb|parindent = 0pt|, but
now this uses the \verb|parskip| package.

\begin{enumerate}[labelindent=0pt,labelwidth=1.25em,leftmargin=!]
    \item This is list one first item.
    \item This is list one second item.
    \item \ldots
    \item[9.] This is list one ninth item.
    \item[10.] This is list one tenth item.
\end{enumerate}

\bigskip
If you don't expect to go past 9 then use:
\begin{enumerate}[labelindent=0pt,labelwidth=0.75em,leftmargin=!]
    \item This is list two first item.
    \item \ldots
    \item[9.] This is list two ninth item.
\end{enumerate}

\end{document}