PCR primers are synthetic oligonucleotides that hybridize to the DNA region that it is desired to amplify and promote the initiation of the elongation reaction by Taq DNA polymerase.
This webpage describes the most relevant points to remember in the design of the primers.
Addgene
Important considerations for the design of primers to obtain a specific amplification with high yield.
PREMIER Biosoft
Details several types of primers, including universal primers, specific primers, degenerate primers and fluorescent-labelled primers.
PCR knowledge