The way I sotre mine is in lever arch files, grouped by family name. As each chidlmarries, another divider with yet another name goes in. Quite easy to find. Birth, Marriage and Death Certificates are in separate files, one for each kind (I do have rather a lot) and again, under the family name. I don't usually have diffculty in finding anything - at least if it is finled correctly.
I think it is true to say that we each have our own ideas, the same idea does not work for every individual. I pinched my idea for certificate storage from a distant relative - prior to that I had them in the same file as basic information. I find the sparate method much easier as I can find a certificate much more quickly.
Shortie