To simplify the code logic and make some of the column values easily accessible on the client, r.a.d.grid can expose them client-side.
To enable the serialization of column values of your choice, you should set the ClientSettings -> EnableClientKeyValues grid property to true. Thus you can extract the respective field value for row through the KeyValues array (attribute of the RadGridTableRow class) passing the unique name of grid column.

Note that this column name has to be part of the DataKeyNames array of the MasterTableView/GridTableView.
This approach is suitable mostly for extracting primary keys client-side.
[ASPX/ASCX]
<script type="text/javascript">
   function RowSelected(row)
   {
    document.getElementById( "<%= Label1.ClientID %>").innerHTML = "<b>CustomerID: </b>" + row.KeyValues["CustomerID"];
   }
</script>

<radG:RadGrid id="RadGrid1" GridLines="None" EnableAJAX="true" PageSize="10" Width="97%" AllowPaging="true" AllowSorting="true" runat="server" Skin="3D">
     <MasterTableView DataKeyNames="CustomerID" />
     <ClientSettings EnableClientKeyValues="true">
     <Selecting AllowRowSelect="true" />
     <ClientEvents OnRowSelected="RowSelected" />
     </ClientSettings>
</radG:RadGrid>

The other available approach is to fetch the values from the grid cells through the GetCellByColumnUniqueName(rowObject, columnName) method. Further info about this can be found here.