Offline - Who do you address?

So with the whole offline scence, sending letters, reports, postcards and what not the only slight problem for me is, who do we actually address the letter and package to?

Most of the people potential clients ive seen (well all I think really) have no information about WHO runs it. Theres just no information like that.

So would you just address it to the company? "Dear XYZ firm" and on the envelope "XYX Firm, Address, ZIP"

I either go quite formal and cover all bases by using the XYZ firm or alternatively (and depending on the type of company) I call them as a potential customer or client and try to uncover some more information that way to even get any kind of senior figures name to then address it to

May be calling and inquiring about the responsible person and then sending the letter in his name is better option as it will give a personal touch to the letter.
Just my 2 cents.

Look up the owners name on manta

Im talking more of things like a group of lawyers or an accountant firm. Things that are one off people like a dog groomer or dentist isnt too bad its buts the companys that have multiple people