Depends what you are doing. For optimization you can run your optimization in parallel on more than one processor if you have parallel computing toolbox.
If you have a Simulink model you can run it on xPC target, which can run in real-time, and can therefore potentially run faster than Simulink model.
Eliminating for loops also helps. There are lot examples on the net how to eliminate for loops by using multidimensional matrices.
As Janez Podonbik said, it depends on your application.If you have Multiprocessor CPU you can use parallel processing toolbox. if you have CUDA supported GPU, you can perform some computation on GPU in matlab.
Also, some tip and tricks can speed up your program. I have enclose a published documents about writing Fast Matlab Code.