Select a restriction enzyme buffer that is appropriate for BOTH of the enzymes you are using. See information sheets at front of lab for correct buffer and concentration.
The total volume of all enzymes in the reaction should be less than 10% of the final reaction volume. Enzymes usually are supplied at 10U/ul and 1ul will be more than enough for our digests.
Add components in the following order:
Water
Buffer
DNA
Enzyme I
Enzyme II
An example of a typical 25 ul reaction would be
milliQ water 15.5 ul
10x Tango Buffer 2.5 ul
DNA (200 ng/ul) 5.0 ul
XbaI 1.0 ul
PstI 1.0 ul
Incubate at 37 C for two hours (longer is okay too).
Notes
FasDigest enzymes use a single uniform buffer, and claim to work in 5 min.