What is important when Choosing a Lamp Socket 

Options abound when choosing the best socket for a new lamp or the most appropriate for an old lamp. Ideally the lamp socket should complement the appearance and overall quality of the lamp while functioning in an easy to access manner. Although your local hardware store may have sockets, rarely do they have a range of types, sizes, materials and finishes. Most lamp restorations require a replacement socket similar to what was originally on the lamp. Depending upon the type of socket there may be options enabling you to better customize the lamp to suit your needs.

First know the size socket you need

Determine Lamp Socket Size by measuring diameter of threaded base of light bulb.

	Candelabra Sockets are for small size bulbs with a base diameter that is slightly under 1/2". This size is often referred to as E12. Most lamp sockets, this size, are made of Bakelite/Phenolic or porcelain. They are used on chandeliers, wall sconces, small lamps & night lights.
	Intermediate sockets are not frequently used. They are for bulbs with a threaded base diameter of slightly over 5/8". This size is often referred to as E17. They are seen in some track lighting.
	Medium Sockets also known as Edison Sockets or E26 are for normal size bulbs with a base diameter approximately 1". They are the most common size used in table lamps. There are three main materials used in their construction: Metal - there are two primary categories: Plated aluminum or brass, Phenolic resin, Porcelain (ceramic)
	Mogul Sockets are big using  large bulbs that are approximately 1½" in diameter. This size is often referred to as E39.Theiy are typically used on floor lamps.

Next What Type Lamp Socket

There are a variety of unique sockets in addition to the standard sockets we are familiar with. These socket serve unique purposes for specific lighting situations.

Gone with the Wind Socket connects with a second night light socket to provide various levels of light. The two lamp sockets can be controlled independently or together. Turn knob switch, on Gone with the Wind Lamp Sockets, operates both sockets. One switch turn - lights only top socket, two switch turns - lights only bottom socket and three switch turns - light both the top and bottom bulbs.
Snap-in Nite Lite Sockets have spring clips to hold lamp socket in place. This style is often used in lamps where both bottom and top of lamp light up independently of each other.
Phenolic Husk Lamp Sockets have a unique bottom turn switch design. This practical design can be used vertically or horizontally.
Side Mount Lamp Socket screws onto standard 3/8" lamp-pipe on the side. This special side connection is often used on lamp clusters and wall mount lamps.
Lamp sockets with uno threads enable lampshades and holders with uno threads to screw directly onto lamp socket. Threads are at light bulb-end of lamp socket.
Candle Lamp Sockets are available in a variety of sizes. They are used with a decorative sleeve to resemble electric candles.

Then How you want to Turn Socket On/Off 

There are four basic methods of switching sockets on or off: turn knob, push thru, pull chain and keyless. Each switch type has its own advantages.

	Push Thru Sockets have a short rod that is easily pushed to on or off position
	Turn Knob Sockets have a small knob which is turned clockwise to on and off positions. In addition, this style socket is also available in 3-way designs offering 3 levels of light.
	Pull Chain Sockets are a popular design. The chain typically hangs down inside the lampshade providing an easy to grasp location for switching light on or off. Lightweight lamps may need steadying when pulling socket chain.
	Keyless Sockets must be switched by an external device such as a cord switch or wall light switch.

Appearance Matters

The material a socket is made of should match or blend with the lamp.

Brass: is a strong, long lasting material that is resistant to rust and corrosion. Most brass lamp sockets are polished – shiny. This traditional type is used on many old and new lamps
Antique Brass Lamp Sockets are brass that is darkened to look old. They are useful on vintage lamps as the color harmonizes with many aged materials.
Brass plated lamp sockets are less desirable as the base metal is less substantial than brass and the plated finish tends to wear off leaving an unsightly metal appearance.
Nickel Lamp Sockets require a little extra investigation to know what the base metal is. Nickel-plated-brass lamp sockets are superior to those plated on other metals. The color is a shiny silver. This hue harmonizes well with silver, chrome nickel and glass lamps.
Bakelite/Phenolic are socket shells made of thick black plastic. They were originally used on lamps where the socket was somewhat hidden by the body of the lamp. This plastic type material is known for its resistance to heat, it’s strength, and non-conductive qualities.
Porcelain Sockets are very durable and long-lasting. They are heat and weather resistant. Recommended for outdoor lighting, applications where the socket is facing down, and with high wattage light bulbs.