\begin{tikzpicture}
  \tikzset{
    ->, % makes the edges directed
    >=Stealth, % makes the arrow heads bold
    node distance=5cm, % specifies the minimum distance between two nodes. Change if necessary.
    every state/.style={thick, fill=white}, % sets the properties for each ’state’ node
    initial text=$ $, % sets the text that appears on the start arrow
  }

%CONTENT

\end{tikzpicture}