I wondered for a while, if I want to send a link to a friend of a that displays a specific point, for example, of a field (also known as a pitch here on OSM) that I want a few friends to play football or frisbee this weekend, how would I do it ?

It's a fairly simple request and it's one that I didn't know how to do until today and this deserves a lot more attention in order to make OSM more useful to users including myself.

There's a couple options:

A. Search for the address or name of the place, in nominatium, OSM's search tool, located on the left hand side of osm.org/
For specific places that do not have addresses or have not yet been added to OSM (and this is often the case here in the USA), this can be frustrating and you're out of luck.

You can add a marker almost anywhere you want:

B.
1. Move the map (you can move the map by left-clicking on the map and hold the left mouse button) so that the place that you want to 'mark' is in the middle of your map.
2. Right click on 'Shortlink' the bottom right-hand corner

You'll have a url like: osm.org/go/ZWb9DX4TV--

3. Add "?m" (without the quotation marks) to end of the URL.

Example: osm.org/go/ZWb9DX4TV--?m

Before double-checking that the URL points to the right place, be sure to copy this url to a plain text file or a new window, because after you load it in your browser, the URL is redirected and your new redirected (and much longer) URL in your address box won't have the marker.

4. Your URL - osm.org/go/ZWb9DX4TV--?m - is ready to go and to be sent to friends.

(PS - thanks to richlv in #osm for letting me know how to do this !)