The code below which I found on MSN did not worked to automatically word-wrap a cell:
dataGridView.Columns[0].AutoSizeMode = DataGridViewAutoSizeColumnMode.D
You could also make it, in this way
DataGridViewTextBoxColumn comments = new DataGridViewTextBoxColumn();
{
comments.Name = "comments";
comments.HeaderText = "Comments";
comments.AutoSizeMode = DataGridViewAutoSizeColumnMode.AllCells;
comments.DefaultCellStyle.WrapMode = DataGridViewTriState.True;
this.dataGridView1.Columns.Add(comments);
}