Minecraft – How to use a command block to welcome new players on a server in Minecraft

if you have them spawn 3 blocks above a hidden command block (powered with a simple clock), you could have that command block do something along the lines of /testfor @p ~0 ~0 ~3 keep in mind that i'm not entirely certain if that's the specific thing to test for to check for players... then hook up a comparator from the first command block to a second one running the message command to @p ~0 ~3 ~3 or ~3 ~0 ~3 depending on which direction the comparator faces (and negative alterations would also be used as necessary)