When choosing your chandelier have a good look at the chandelier’s four main aspects that are: quality of metal parts, quality of trimmings, joining of the crystals and electrical wires.
With regards of the metal parts quality in second hand chandeliers you look for the tarnishing.Tarnish is basically discoloration of the metal, most common are rust speckles beneath the varnish so it cannot be wiped off nor can it be polished off with a polish paste.
Good quality chandeliers are made of brass, lesser quality chandeliers are made of all sorts of metal compounds, some of which are prone to rusting.
I do not mean chandeliers made of wrought iron which is craft by itself and could be of high quality depending on the skill of the man who makes it. Brass darkens if left natural so for bright gold finish the brass is lacquered, heat treated and vanished.
Antique gold finish is also completed by vanishing
whereas nickel finish is actually nickel plated and real gold finish is also done by electroplating.
Finishes nowadays are long lasting as long as the procedures are followed correctly as would be done by any reputable manufacturer. Any shortcuts within the finishing procedures will result in premature tarnishing which is mainly caused by humidity and fluctuation of temperature. There is nothing worse for a chandelier then sitting in an unheated garage or a loft where the temperature can vary from -5 to 25 degree C. Not to mention the effect of the varied temperature on a chandelier that is just sitting in a box not suspended as chandeliers were designed for, which unsurprisingly causes metal arms to distort and glass arms to brake. The stress on chandeliers stored incorrectly is great, but more worryingly may compromise integrity of the structure itself and when rehung may end up on the floor or worse injuring someone.
Trimmings quality vary greatly from plastic through glass to crystals. There is not much point talking about plastic trimmings which do not look good with the exception of some hyper modern pieces. Traditional glass trimmings are generally not of as high quality and there is no point of fine finishing as you cannot achieve the great sparkles without PbO anyway unless you are Mr Swarovski. Now for the crystal trimmings, classification of crystal vary from country to country from as little as 5% up to 31% PbO. Good quality crystal contains between 24% – 31% PbO.
There are hundreds of shapes and sizes of these crystals so there is a great selection to choose from.
Exceptionally high quality crystal is made by Swarovski. Swarovski produces two ranges: Spectra which is an unleaded crystal and the best value for quality
and Strass which is 31% PbO and I wouldn’t hesitate to say that this is the best crystal there is.
Joining of the crystals is very important due to aesthetic and holding aspect. The cheapest form of joining is by a ring resembling a key ring, but smaller which is time
effective however after washing you may find rusting which can also discolour the crystal. 
The best form of crystal connectors are made of brass and are in the shape of either a pin twisted into various forms of joins
, an O shape…..
Old chandeliers were joined by a wire simply cut to size, crystals were threaded on and twisted together.
The electrical wiring is only an issue when you are not purchasing from a shop. In this case see if the chandelier works and physically look whether the wire is in good condition and has current colours, then have it tested by an electrician. Electricians will not install a chandelier with bad wiring as the danger from electrical fires is not something one would wish to be responsible for. Rewiring is time consuming and a smallish 6 arm chandelier would cost you around £160 so bare this cost in mind.
Over the years I have learned that if an item is cheap it looks cheap, but if it makes you happy then buy it anyway. But do have a good look around first so you can make a more informed decision.
