How do you find out what sort of memory to buy for your notebook?

I dont know what sort of pc I hold.

How do you find out what sort of memory to buy for your notebook?

go to http://www.crucial.com and run the system scanner. Quick and painless.
be in motion to your computers manufacturers website and look up the specs for your model.
What you could do is shift to a store were they put on the market electronics for example best buy and ask for the people that know about computer or you could contact Queeksquad or Fire something. So yeah