Microfossils can be extracted from almost all fossiliferous sedimentary rocks - unconsolidated marine sediments being the most productive. The scientific value of the extracted fossils depends on the care taken in their extraction. It is essential to avoid contamination of the sample, which should be labelled clearly and securely in the field. The re-use of sample bags is not recommended and sieves should be thoroughly washed between processing sessions.

Unconsolidated clays, silts and fine sands are most easily processed and often yield rich and varied assemblages of well-preserved fossils. The sample should be dried thoroughly, then soaked in hot water to disaggregate the sediment. The resulting 'slurry' should be wet sieved. A dispersing agent such as 'Calgon', dissolved in the water at the soaking stage, can be helpful in breaking down the sediment. The 'dry/soak/sieve' cycle should be repeated two or three times to obtain a clean sample. It is worth taking trouble at this stage as it makes life so much easier later on.

Eight inch diameter brass test sieves are recommended for sorting the residue though these are very expensive. As an alternative, one can make sieves or buy cheaper sieves, though these are unlikely to last as long as the better quality product. Sorting of residues is made easier if a graded series of sieves is used; preferably with the aperture of each succeeding sieve being about half that of its predecessor.

Finally, the chosen sample should be sprinkled sparingly onto a picking tray. Using a microscope, preferably a binocular stereo model with magnification of 10x to 40x, selected fossils are removed using a damp artists' brush (size 000 or 0000 recommended) and are placed in a multi-cell slide for study.