One of the quick technic toward problem solving or optimisation.
B - Bottleneck. [The part which slow down the overall runtime]
U - Unnecessary Work. [Doing unnecessary check on something which is proven that does work or does not work.]
D - Duplicated Work. [Similar or repeated logic being used]
Use above most common things to figure out that waste most of your time during designing or problem solving. Once identified make effort to get rid of it.
If you still feel optimisation is still lacking - There is no restriction: you can repeat this approach.