reduce esr
You parallel two or more capacitors. If the connections are short, you will lower the total ESR. The total ESR is calculated simply as the parallel equivalent of the individual ESR's.
This is easy to see in the case of equal caps with equal ESRs. You have two or more identical series RC networks, all in parallel. Since the R and the C portions are equal, the junction points (where the C and the R are connected together) will be at the same potential for all networks, since they are in parallel and the elements are identical. Since all those nodes are all at the same potential, you can short them together.
But when you short those points together, the C's are all in parallel and so are the R's. Therefore, the total capacitance is the sum of the individual capacitances and the total ESR is the individual EST divided by the number of caps in parallel.