Porte Maillot to Place de Tertre Montmartre

Metro line 1 from Porte-Maillot to Charles de Gaulle Etoile. Metro Line 2 to Pigalle. Metro line 12 one stop to Abbesses. Fare: €1.60.

If you will have luggage, that is a lot of metro changes, though it is the cheapest way. I'd be tempted to take a taxi and hang the expense.

Ellen -

Porte Maillot - Line 1 to Concorde (Direction Chateau de Vincennes) - change to line 12 (direction Porte de La Chapelle) to Abbesses will give you minimal station change. It is a bit quicker of an interchange than at Charles de Gaulle Etoile as previous suggested as well. May be perhaps a little longer in time but not much - plan on about 25 minutes or so.

There is a set of stairs to head down to line 12 at Concorde. If you station yourself at the front of the train on Line 1 it will give you a little head start ahead of the others.

You can also take the route that Tim suggested but walk from Pigalle - given you have luggage it may not be preferred has a bit of an uphill and longer than you might like.

Since Place de Tertre is north of Abbesses, take Jona's route to Abbesses if you want to make one one transfer rather than the route I gave which requires two transfers.