Saving Documents in Libre Office

Hi,I hope this is the correct place to ask this question?.
Well here goes anyway.
I use Libre office for all my documents and spreadsheets etc,Now the problem is when composing a document in Libre office then send it off to a friend who don't use Libre office.
He has Microsoft office so he cant open my document,What I really would like to know is what format should I save my documents in Libre office so that they can be read the other side with Microsoft office?.
Or would it solve a lot of hassle if I installed Microsoft office,I'm running windows 7 home premium.
Any help Please its causing a lot of problems between me and my local newspaper editor,Its not on a big scale just now and again I write about some old news and old photographs of where I live.

Help PLEASE.
Thanks.

Yea thanks for that.One other point.
I have about fifty documents in Libre format,Would it be possible to convert these from Libre to Microsoft all together or will i have to convert one at a time?.

Thanks.

Well,Many thanks for the info and the help you gave me.But have decided to get rid of Libre office as its been giving me a lot of agro as with regards sending libre documents to people and finding that they cant open them.
I was under the impression that libre office and open office was compatable with microsoft word,But found out the hard way it wasn't the best option to go down.

Now have gone and installed the microsoft office starter,Looks okay to me will do what I want it to do.It will do word documents and simple spreadsheets etc,Dont want the power point part of it to complicated for me.

Well many thanks for all info once again.
have a nice day,Very wet and cold here.
Diolch yn fawr.