Like most things in life, it is better to be prepared. Have some chains with you and know how to put them on. However if you don't feel like being prepared, don't worry this is America, with a little bit of money you'll be taken care of. Most chain control areas have people that will install chains, cost is between $20 and $30. Many chain control areas are located near stores or gas stations that will also sell you chains, cost between $30-$150. Do not however bank on this. Many of the smaller chain control check points do not have such luxuries. Often times you need chains simple because you are stuck on an icy hill where there is no one around to help you out.
So you are going to the mountains this weekend to ski. There is a snow forcasted. What chains should I get? The term "chains" is generic. It refers to a traction deceive mounted on the drive tires of an automobile. In fact chains can either be comprised of chain links, or cables. The general rule of thumb is that you run cables for vehicles with limited clearance between the tires and wheel wells or smaller cars. You run chains when there is a decent amount of clearance or for larger vehicles. Basic tire chains have a ladder type constructions. Two long length of chain which wrap around the tire make up the uprights of the ladder. The cross links which go across the tread of the tire are the ones that are driven on, make up the rungs of the ladder. These types of chains are the most common, cost the least, and when they are made of actual chain material are the most serviceable/repairable.
If you are trying to decide between basic chains or cables, my preference is chains. They provide much better grip, and last longer. The downside is that they require a little more wheel well clearance. Might cost a slight bit more. Might not be as user friendly because they can get twisted up. And if you happen to break a cross link, and decide not to stop to fix it, can do more damage to the inside fender liner.
My biggest fault with cable type "chains" are the rollers. If you look closely at the pictures cable type chains, you will notice that the cross links have small rollers fished through the cable. Sometimes these rollers are not solid and made of a spring like cylinder. Why rollers, two reasons. One-increased diameter. The diameter of the cables are very small, and do not provide much grip. Adding the rollers increase the amount of bite into the snow. The second reason is to actually decrease traction. Cables are easy to break. If you drove on something that gave you solid contact such as a bumpy dry road, and hit the gas; the cross link of the cables can easily snap.
Basic ladder type chains are often the only thing available for purchase when you need them. They work, but are not without their problems. Three main problems exist with this type of chains that will make you consider buying a fancier set of chains. 1-installation. They are difficult to install. Most will need you to drive over a section of the cross link, and you also need to get behind the tire. 2-rough ride. Since you will only be on one chain cross link at a time and intermittently, ladder style chains yield a bumpy and loud ride. 3-poor traction. Again, since you are on the chains only for a fraction of the time, and your tires the rest of the time, you do not get the full benefit of running chains.
Z Cables and Alpine/Euro Chains If any product is titled "basic", you as the reader surely knew that a "fancy" was coming up next. These two types of chains have the benefit of easy installation and better contact patch. The contact patch improves both smoothness and traction.
In my opinion the Alpine Sport chains are the best on the market. They go by many different names, including: Alpine Premium, and Euro Chains. They have a split design which allows you to install the chains without needing to drive over them. The chains do not use standard ladder type cross links, but are diamond patterned. The diamond pattern insure that most of the time you have a section of chain between your tire and the ground. This also give a very smooth ride. The chain links are a square profile, and give good grip. They are also low profile, and should work for most vehicles, even those with limited wheel well clearance. As a bonus most of of these type of chains have a built in tensioner. These chains do cost more and is not always available at your corner store or gas station. If I was to recommend a set of tire chains these would be the one.
Finally there are the Z chains. I sometimes refer to these as the Highway Patrol chains, since these are the ones that the cops run on their cruisers. Z chains are in fact cables. I am not a huge fan of these chains, but they are a step above regular ladder style cables and are worth mentioning. These chains are available more often then the alpine sport ones. These chains have two major advantages. One is the diagonal contact which increases the duration of contact between the tire and the ground. The diagonal orientations also provides some lateral traction for cornering. Most Z chains also have a split design which makes installing a breeze. The split refers to the fact the cross link array have a break. Therefor you can attach the rear hoop, then pull the two "halves" around the tire and connect the two attachment points. Z chains also use spring coils instead of solid rollers which provides a bit more traction. My greatest fault with the Z chains is that they rely heavily on the rubber tensioner to keep the chains tight. There is limited static adjusted. Though these are slightly lower profile than the Alpine sport chains, due to the fact that they are held on by elastic tensioners, they tend to fling out at higher speeds and negate their low profile advantage.
This article barely scratches the surface of the topic of chains. More can be discussed on installation, tensioning, chain link variation... However this is enough to get most people started. Good luck and enjoy the mountains!