Limpar todos os Edits, Memos, MaskEdits, etc...

procedure LimpaEdit (Form: TForm);
var
i : Integer;
begin
for i := 0 to Form.ComponentCount - 1 do
if Form.Components[i] is TCustomEdit then
(Form.Components[i] as TCustomEdit).Clear;
end;

O Componente Checklistbox

//limpar
checklistbox1.Clear;
//adicionar itens
checklistbox1.Items.Add('Item');
//Verificar os ítens checados
for a:= 0 to checklistbox1.Items.Count-1 do begin
if checklistbox1.Checked[a] then
listbox1.Items.Add(checklistbox1.Items[a]);
end;