There are many publications you can refer to for methods.

Here is a kit for doing this:

http://www.epibio.com/docs/default-source/protocols/peripreps-periplasting-kit.pdf?sfvrsn=6

Here is a protocol that uses osmotic shock:

https://web.stanford.edu/~loening/protocols/Osmotic_Shock.pdf

The methods assume you are interested in soluble proteins, of course.

Thanks sir