Display coordinate system

I was facing a similar problem and on this post I found the solution. But to clarify the whole "How To" a little better, I want to contribute my solution here:

 public void OnDrawGizmosSelected()
 {
     // draw y axis with arrow
     Gizmos.color = Color.green;
     Gizmos.DrawLine(transform.position, (transform.position + (2 * transform.up)));
     Cone.DrawCone(transform.position + (2 * transform.up), transform.up, 0.1f);
 
     // draw x axis with arrow
     Gizmos.color = Color.red;
     Gizmos.DrawLine(transform.position, (transform.position + (2 * transform.right)));
     Cone.DrawCone(transform.position + (2 * transform.right), transform.right, 0.1f);
 
     // draw z axis with arrow
     Gizmos.color = Color.blue;
     Gizmos.DrawLine(transform.position, (transform.position + (2 * transform.forward)));
     Cone.DrawCone(transform.position + (2 * transform.forward), transform.forward, 0.1f);
 }
 
 
 private static class Cone
 {
     private static Vector3[] newVertices = new Vector3[]
 {
             new Vector3(-0.0f, 1.0f, 0.0f),
             new Vector3(0.2f, 0.0f, 0.4f),
             new Vector3(0.5f, 0.0f, 0.0f),
             new Vector3(0.0f, 0.0f, 0.0f),
             new Vector3(-0.3f, 0.0f, 0.4f),
             new Vector3(-0.5f, 0.0f, 0.0f),
             new Vector3(-0.2f, 0.0f, -0.4f),
             new Vector3(0.2f, 0.0f, -0.4f),
 };
     private static Vector3[] newNormals = new Vector3[]
     {
             new Vector3(0,1,0),
             new Vector3(1,0,1),
             new Vector3(1,0,0),
             new Vector3(0,-1,0),
             new Vector3(-1,0,1),
             new Vector3(-1,0,0),
             new Vector3(-1,0,-1),
             new Vector3(1,0,-1),
     };
     private static int[] newTriangles = new int[]
     {
             0, 1, 2, 2, 1, 3, 0, 4, 1, 1, 4, 3, 0, 5, 4, 4, 5, 3, 0, 6, 5, 5, 6, 3, 0, 7, 6, 6, 7, 3, 0, 2, 7, 7, 2, 3
     };
 
     private static Mesh mesh;
 
     static Cone()
     {
         mesh = new Mesh();
         mesh.vertices = newVertices;
         mesh.triangles = newTriangles;
         mesh.normals = newNormals;
     }
 
     public static void DrawCone(Vector3 position, Vector3 rotation, float scale)
     {
         Gizmos.DrawMesh(mesh, position, Quaternion.FromToRotation(Vector3.up, rotation), new Vector3(scale, 2 * scale, scale));
     }
 }

Witch this code block you can easily draw a coordinate system. Just attach this to a GameObject and you will have a coordinate system drawn to it's origin using gizmos. To make this coordinate system visible in the game view you will need to enable gizmos there.