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Optical Techniques
Detection of fingerprints starts with optical techniques -- the application of special kinds of lights -- as they will not prevent the use of further detection techniques. "Luminescence" techniques also may be attempted later in conjunction with physical or chemical methods, but they should always be the first attempt. Lamps that provide light at a wide range of wavelengths (from infrared to ultra-violet) will yield the best results. Lamps used most often by forensic investigators are high-intensity, filtered arc lamps, like the "Polilight" used by the Australian Federal Police.
Porous or Nonporous Surface?
If luminescence techniques don't work, an assessment of the kind of material the prints may be on will be critical. Fingerprints on a porous surface, such as paper or cardboard, will be different from those left on a nonporous surface, such as glass or metal. The surface type will dictate the chemical and physical agents to use next.
Chemical Techniques for Porous Surfaces
When testing a porous surface like paper, the best technique for revealing latent fingerprints will probably be the application of the chemical reagent 1,8-diaza-9-fluorenone, or "DFO." After dipping the paper in a DFO solution, leave it to soak with some gentle heating device, like a space heater, for 24 hours. The leftover amino acids in the prints ought to become highly luminescent with optical-detection techniques.
Physical Developers With Porous Surfaces
Application of physical developers can achieve further fingerprint detail. You will dip the fingerprints in water-based solutions, which are "physical" developers because, instead of reacting with leftover chemicals in the fingerprint, the developers will deposit a layer of silver on top of them. The solution is a mix of silver nitrate, citric acid, iron components, and a few other water-insoluble ingredients that catalyze the silver deposits.
Physical Techniques for Nonporous Surfaces
On the other hand, if you have latent fingerprints on a nonporous surface, like glass, plastic, metal, and gloss-painted surfaces, and the luminescent techniques have failed, you'll want to try developing them with fingerprint powders. Though they represent one of the least sensitive fingerprint developers, these powders are also some of the most cost-effective methods (hence their common usage by forensic investigators). Aluminum-flake powders applied gently with a fine brush are thought the most sensitive, while magnetic powders, applied without a brush, are considered the least destructive to the print.
Another method that is very sensitive is the vacuum metal deposition technique. If you can secure your surface in a vacuum, coating it with a layers of zinc and gold will usually leave the substrate surface around the prints penetrated by the zinc while the prints themselves are infused by the gold. This method is considered one of the most effective for treating nonporous surfaces, even with fingerprints as old as 6 months, but the materials required are quite expensive.
Chemical Techniques for Nonporous Surfaces
A chemical option for revealing prints on nonporous surfaces is the cyanoacrylate fumigation technique. This chemical, related to quick-setting "superglues," can be pumped into a room as a vapor and will leave deposits on the fingerprints that then show up extremely well under luminescent techniques.