There are 3 common types of fingerprints taken at a crime scene:

Visible prints: such prints are made by fingers touching surfaces after they have been in contact with a coloured material such as blood, paint or ink and so on.  These are easy to identify.

Plastic prints: such are made when impressions of the prints are left in soft materials such as putty, soap or dust and so on.  As with the visible prints these are easy to identify.

Latent prints: made by the transfer of oils and/or perspiration present on the ridges onto the surface.  These are hard to identify.  If they are found on surfaces like glass they are usually brushed with a power and then lifted using adhesive tape.  Also fuming super glue can be used.  Prints found on paper and other porous surfaces are sprayed with ninhydrin which reacts with the amino acids presents in the perspiration and turns to a blue-purple colour.  This takes upto 2 hours but the process can be quickened by heating the sample to 80-100°C.