uniqueness : ensure correct priming site
Length : 17-18 bases
Base composition : average (G+C) content around 50-60% ; avoid long (A+T) and (G+C) rich region
Melting Tm between 55-80 C are preferred
Optimize base pairing: it's critical that the stability at 5' end be high, Low specific binding at the 3' end
Absence of significant hairpin formation
Absence of dimerization capability