How to share Garmin waypoints?

I have a new Garmin eTrex and am playing with downloading my waypoints from the device in the Mapsource software. Seems pretty easy and I like being able to use my keyboard to change names, etc. Which of the many Mapsource file formats would I save my waypoints to if I wanted to share them with someone?

There are mps, dxf, gdb and gpx file extensions. I assume I would just send an email and attach the file, then my friend can use his Mapsource software to open the file and import the waypoints into his Garmin unit. Is that how it works?

I have mapsource also....I can double click the saved waypoint and change the name and other fields. My software defaults to gdb extensions. I am thinking you can save the waypoint file under any name to your hard drive. Then just email this file to your friend. Once he opens his Mapsource file...he should be able to import that file to his Mapsource by going to file...open and then to the location of his saved file. I have never tried it, but see no reason it should not work this way.

save' then attach as gpx. I know this works.

Thanks guys. All that is helpful.

So assuming I keep all my fishing waypoints in one MapSource file, how would I send someone my waypoints for a specific lake? I only see how to send them the entire file of all waypoints/routes/tracks I save.