In the hobby of model railroading a key consideration before getting started is scale. There are several different modelling scales or sizes to choose from. It is key that you choose one scale for your layout otherwise your layout will appear very unrealistic with oversize and undersized scenery. Most commercial products will have the scale listed on the box. Currently the most popular scale is HO scale which has been the case since the 1960s when HO overtook O scale (the same size as classic Lionel trains). Most hobby shops stock a wide variety of HO scale equipment and it is possible to build a complete layout with commercial equipment bought off the shelf.
HO scale is 1:87 meaning every prototype is eighty seven times larger in scale. If you have a model of a forty foot boxcar for instance, stringing eighty seven models together would come out somewhere near forty feet, or the size of the real boxcar. HO means “half O.” It must be noted that this does not refer to the scale (otherwise it would be 1:96 considering O scale is 1:48) but instead the gauge, meaning the distance between rails. HO scale rails are exactly half as far apart as O. HO scale’s popularity owes to the fact that it is large enough to show detail while small enough to fit into limited spaces. Larger scales take up more room than all but a few modellers are lucky enough to have and layouts are fairly limited for most. Smaller scales, while more can be fit into a given area, have less detail and are more difficult to work with. HO scale is dominant as a result of compromise. Over the years its popularity has led to more manufacturers offering more materials. While there is no “best” scale HO scale is certainly the easiest for the beginner due to the wide variety of products available and indeed many beginners end up in HO scale simply as a result of the fact that most starter sets are HO scale. Because of its ubiquity, HO scale is one of the more affordable scales.
HO scale has advantages and disadvantages. Its primary advantage is that it is quite possible to find a ready to run model of virtually every locomotive used by a class I rail road over the past century in North America. There are three primary types of power for HO scale trains, DC, AC, and DCC. DC simply delivers the current through the rails and the engine moves forwards or backwards depending on how much power is delivered to the rails. This is the simplest method of operation and the cheapest, but wiring can get complex if operating more than one locomotive. European made trains often run on AC and feature studs embedded in the tracks in place of a third rail. DC and AC engines are incompatible. Increasingly DCC (digital command control) is a popular option. DCC is more expensive than DC but it allows you to control multiple engines at the same time with one unit. The fact that so many ready made DCC engines are available is another draw of HO scale. Bachmann’s DCC system is to be recommended for beginners, and I myself use this system. It is simple and suited for small layouts with ten trains or less. HO scale also has a huge variety of scenery and structures available for your layout, some of this comes in kit form whereas others are pre-built. Kits are usually much cheaper though.
HO scale’s main advantage, its compromising nature, is also its primary disadvantage. For modellers who will not compromise on their desired goals it may not be the best choice. If one wishes to run prototypical length trains, particularly from the modern era where long trains are a rule, even HO scale is impractical unless one has a huge layout. For those with virtually no space at all, HO scale may even be too large making N a more desirable scale. On the flip side, modellers who demand a high amount of detail may find HO scale frustrating. While considered a middle of the road scale, HO scale parts are still quite small to handle. They break easily if one is not careful, unlike rugged O scale trains which still run well after sixty years with a little bit of oil and cleaning. In spite of its disadvantages I myself am currently in HO scale. I prefer O scale and have some O equipment but it is simply too large for my limited space. HO scale is by far the easiest to work with because of its size compromise and the sheer amount of production material available. There is no right or wrong way to model, but many modellers will end up in HO scale because its compromises will outweigh the disadvantages of other scales.
As an addendum I will include some words on a related scale as well as narrow gauge modelling. You may have heard of OO scale. OO and HO scale are compatible (they run on the same track) but OO scale trains are sized to 1:76 and thus the wheels are slightly closer together than in real life. Most OO scale trains are British prototypes as British prototypes are often smaller and early drive mechanisms would not fit inside. OO scale is the most popular scale in Britain, one of only a few countries where HO scale is not dominant. The difference to the naked eye is fairly small. In fact British trains at 1:76 sometimes appear smaller than large North American prototypes at 1:87.
Narrow gauge modelling, meaning modelling of railways smaller than the standard for feet, eight and a half inches between the rails, also has a following. These will often include a lower case n after the scale label. HOn30 for instance is narrow gauge (n) and modelling two and a half foot railroads (30 inches). Most narrow gauge railroads in the USA were three foot gauge with the notable exception of the famous Maine two footers. HOn3 is a minority among narrow gauge modellers, however, for one simple reason. HOn30 runs on N scale track and thus is compatible with N scale equipment in terms of trucks, kitbashing etc. making it much easier to use. Though two and a half foot railroads were rare many find it a decent compromise when modeling either two or three foot railways since the difference in terms of a model locomotive is actually quite small to the eye. More discriminating modelers will find more realistic scales to their liking, but this will require some skill with scratchbuilding and conversions.