If you are S-curious, you do not need to ditch your existing models and layout. Start off small. Buy an S-scale box car, ready-to-run or a kit. See if you like the size. See if you can see the details better.
If you are interested in seeing S-scale in person, consider looking for an S-scale club. Click on the "Clubs" button, and look for one near you. Contact the club to see if they have an upcoming club meeting or show. Clubs will welcome you and be glad to show you around. Most clubs have meetings at members' homes, so you will be able to see their layout in person, if they have one. You might also see if there is an upcoming model railroad show in your neck of the woods, by clicking on the "Events" button. We try to list only shows that have or are likely to have an S-scale presence (club layout, S manufacturer, etc.).
If you already have some A.C. Gilbert American Flyer equipment, and you wish to continue to expand your collection or to start operating (i.e. build a layout), your best choice is the secondary market (e.g. eBay, various discussion groups, clubs, consignment dealers, and estate sales). Rare items show that in their pricing, and common items should be easy to get. You will definitely want to get the Greenberg's American Flyer Pocket Price Guide published by Kalmbach every year (available at many retail stores, as well as online at places such as Amazon and Barnes & Noble). For track, if you want to remain pure A.F., you will have to, again, look at the secondary market. GarGraves makes track that looks like the original A.C. Gilbert track. However, if you are OK with getting more scale-looking track, you can buy new track from Lionel, MTH, Fox Valley Models, and American Models. These all use rail that is tall enough for AF equipment. On the secondary market you may also find some S-Helper Service track components. For a complete listing of what is available, be sure to click on the Resources button.
If you are interested in building a layout that combines both original A.F. and the more newer products, you will want to look at locomotives and cars that are truly AF-compatible. All Lionel and MTH products are AF-compatible. Other companies, such as American Models, make equipment that can be ordered with AF-compatibility. You can buy the same track components mentioned above.
If you are a pure scale modeler, most of the A.C. Gilbert-era American Flyer (i.e. pre-1969) does not apply, unless you want to spend time converting the equipment. MTH (which bought the former S-Helper Service tooling) makes it easy to convert their AF-compatible equipment to scale. Couplers and wheels are sometimes provided in the box, and pre-drilled holes in the underframe for Kadee-style couplers are usually provided. Some retailers will even do the conversion for you, if so requested. You can order equipment from American Models in either "scale" or "AF-compatible" (be sure to look for "DC", i.e. direct-current, equipment; "AC" current is compatible with older AF-style layouts). Newer Lionel equipment is mostly convertible to "scale", but some items require more work than others. Their freight cars may be as easy to convert as MTH's, but if you buy a "hi-rail" (which is another term used to describe AF-compatibility) locomotive, the wheels come with deep flanges. These may require custom work (or replacement) to make them compatible with scale track. So, if you are looking at Lionel engines, be sure to check that they have scale wheels or that scale wheels can be bought separately, which is something Lionel has been offering on some of their engines since about 2012. There are also several small manufacturers that make S-scale equipment. Most of these usually default to making "scale" equipment, or they simply do not provide the trucks and couplers, so that you can choose for yourself.
Most modern S-scale engines use motors on par with HO-scale equipment. So, for DCC systems, you can treat S-scale engines as you would HO-scale engines. The motors will work with any DCC decoder on the market (sound or not) that is compatible with HO-scale equipment.
One reason for the existence of the NASG is to bring people together who have a common interest in modeling in 1:64 scale. Whether or not you are an NASG member, the NASG's regional vice-presidents are here to help you with whatever questions you have. If they don't have the answer themselves, they certainly have the contacts to get you the info.
Contact the Eastern Vice President, if you live in Delaware, Connecticut, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, Virginia, West Virginia, The District of Columbia; the Provinces of New Brunswick, Newfoundland and Labrador, Nova Scotia, Ontario, Prince Edward Island, Quebec; Continental Europe; Continental Africa.
Contact the Central Vice President, if you live in Alabama, Arkansas, Florida, Georgia, Illinois, Indiana, Iowa, Kentucky, Louisiana, Michigan, Minnesota, Mississippi, Missouri, North Carolina, South Carolina, Ohio, Tennessee, and Wisconsin; the province of Nunavut.
Contact the Western Vice President, if you live in Alaska, Arizona, California, Colorado, Hawaii, Idaho, Kansas, Montana, Nebraska, New Mexico, Nevada, North Dakota, Oklahoma, Oregon, South Dakota, Texas, Utah, Washington, Wyoming; the provinces of Alberta, British Columbia, Manitoba, Northwest Territories, Saskatchewan, Yukon; Central America, South America, continental Asia, Australia, New Zealand, Pacific Rim and Pacific Island Nations.
There are also discussion groups, forums, and other web sites that may be of help to you, especially if you have a specific question. To get the full and up-to-date listing of these, click on the "Resources" button, and scroll to the bottom of that page.