Scale is important

There are a few points that you will need to keep in mind. First understand that scale is generally the reduced version of what the original will look like. The most common ones used is the HO version. This is in the 1:87 ratio. Almost 70% of rail modelers use this. There are several versions of this that are available such as Hon3 and Nn3. These are narrow gauge versions. This basically means that the space between the tracks is much less.

The reason HO is popular is because its size makes it convenient for home based layouts. Any other scale becomes too small for great models. The most common of layout space is 4' X 8' and the HO is best suited for it. There are however other scale such as the N (1:160) or O(1:48) or even G(1:24) and Z(1:220). There are several other scale available, but not always are these easily found.
 
If the HO is not something that works for you then the N scale is what you should consider. This is almost half the size. The challenge with the HO is actually setting it up and detailing it. While it is difficult, it is not impossible.
 
If you are lucky enough to have enough of outdoor space to create a railway layout then you should think of going in for larger trains on the O or G scale. These range in the 1:24 or 1:48 proportions. Detailing spectacular pass-throughs such as gardens and falls are easily done with them. Most modelers find the HO scale of 1:87 most easy to work with. They don’t take up too much of space and detailing them is the easiest.

Also you will need to settle on the theme of your model railway layout. This is the best way to able to decide on your color schemes as well as the style of your accessories. There are several themes across several time periods that you can choose from. Its easy to try and replicate any.