Low quality wood file cabinets are usually sold for customer assembly. For some people, this can be problematic and the use of cam hardware is necessary. It is advisable for consumers to avoid file cabinets which are made of particle board (which is often advertised as wood), as these are not very durable. The Furniture Manufacturer's Association does classify particleboard as solid wood, but what you want is the real thing - solid pine, cherry or oak wood.
You should remember that a file cabinet generally needs to hold a relatively large amount of weight; so you need glue screw and clamps to hold things together, not cam locks set in particleboard.
Oak Veneer Bookcase
You should know the difference between solid wood, printed grain and genuine wood veneer. You can tell if furniture is composed of solid wood by looking at the grain. If the grain on the end runs perpendicular too the rest of the grain, then what you have is most likely veneer rather than solid wood. While veneer has its place, solid wood is what you should be looking for in a file cabinet. Don't let yourself be fooled!
A wooden drawer should be made with English Dovetailed Joints rather than cams, which are not likely to be able to hold together when the cabinet is loaded. Glue and staple can work, as long as the staples are only there to hold things together until the glue has dried.
The hardware which is responsible for opening and closing the drawers is also important - does the drawer pull out evenly and smoothly? Is the drawer properly fitted into the track? If you can't pull out at least 90% of the drawer, then you are losing storage space and it will be hard to retrieve items from the back of the cabinet. Don't purchase a file cabinet which uses Euro type roller glides, these will not be able to hold up to the weight of a loaded file drawer (these glides are made with two interlocking wheels on a spindle - check for this style when looking at a wood file cabinet). A ball bearing full extension slide system which is rated to support at least 100 lbs is best for file drawers.
Finally, think about whether you will want these drawers to be lockable. You should be able to place locks on individual drawers; you can also choose a system which allow one-key locking and unlocking of all the drawers in the cabinet. An interlocking system can be costly to install in a quality wood file cabinet, so be aware of this.
When looking at file cabinets, take all of the above into consideration. Look for solid wood construction and glides which can actually stand up to the weight of a loaded cabinet and you should do well and have a file cabinet which will serve you well for years to come - especially if you avoid self-assembly file cabinets.