Les Puces de Saint-Ouen – www.marchesauxpuces.fr
This darling of the guidebooks is a good start to start the antique hunting.  Topping the list of 'world's largest markets', this massive, website-boasting market is a collector's paradise. Covering an area of seven hectares, it's actually a collection of fifteen flea markets comprising about 3000 stalls.  Being the obvious place for bargain hunters (receiving an average of 150,000 visitors each weekend), it has its pluses and minuses.  On the upside, you really do get some lovely stuff here.  It’s an inspirational place.  And, if you actually happen to know stuff about antiques and speak good French then you might find something interesting.  On the downside, if you know nothing about antiques and are blatantly a tourist then the stall holders, pros that they are, aren’t really that interested in you. Also, prices here are going to be higher than elsewhere.  Nevertheless, the visual spectacle is worth it.  

Les Puces are open Saturday, Sunday and Monday from 9am until 7pm.  Things to bear in mind: Mondays are far quieter, but on the other hand there are fewer stalls open.  People start packing away at about 6pm.  As is the case where the tourists congregate, there are pickpockets about – keep an eye out.

Le Marché aux Puces de Montreuil – Avenue de la Porte de Montreuil
Taking it to the other end of the antique shopping spectrum, le Marché aux Puces de Montreuil has more of a car boot sale vibe.  There’s plenty of junk here, in which you’ll find just about everything from used car parts to 1940s-era dresses to old crockery.  It can be a bit dusty and grimy, but it’s worth a root around in here because the gems are hidden.  You’ll also get far better bargains here than in most other markets.

Porte de Montreuil market is open Saturday, Sunday and Monday from 7.30am until 6pm.  

Marché Richard Lenoir – Boulevard Richard-Lenoir, 11th Arrondissement
This market is mostly known for its food produce on Thursdays and Sundays, but on Saturdays the market is turned into a sales ground for local artists.  If you’re looking for something unique and interesting to add to your home then having a wander around here from 10am until 7pm on a Sunday is a good idea.  For more details, check out their site: www.artistesparisbastille.fr

Marché aux Puces de la Porte de Vanves – Avenue Georges-Lafenestre/Avenue Marc-Sangnier, http://pucesdevanves.typepad.com.   
Another famous one to round off with – Porte de Vanves is big and well known, but much more down to earth than the Saint-Ouen market.  It’s full of bric-a-brac stuff for your house, rather than for clothes.  This place is more about kitschy and cool than elegance and grace, but you are far more likely to find something here which you’ll actually buy than in Saint-Ouen.  It’s a weekend market, running from 7am until 1.30pm on Saturdays and Sundays, but people start packing up around 12pm.

And the big point to remember... Haggling
This can’t be stressed enough: stall holders are used to haggling, in all of the above markets.  Don’t get involved in haggling unless you will want to buy the piece when you’ve come to an agreement; decide in advance what is the maximum you are willing to pay; and don’t offer less than half (more like two-thirds) of the asking price as your starting bid – it’s just insulting.  Don’t be aggressive for much the same reason.  But apart from that, feel free – it’s part of the process.