You need one wireless connection. If you have an ethernet connection for Internet, that is even better.
LD560,
LiquidAngel,
Nintendo3dsDude In short - just wait, if maccheck.cmd gave you not all zeroes in the first string, you will get homepasses more or less - it depends on the second string.
Long explanation: there are two possibilities of getting a homepass.
First, you have set exactly the same MAC and got streetpass data previously stored for that MAC from the other 3DS. The problem is that there are a number of different drivers which modifies MAC address in different ways, so in that case you only be able to get s streetpass from the same nzone.exe user with the same wireless driver as you and there is nothing can be done (well, actually there is the way and that is bacause I'm asking to send me a full maccheck.cmd output to gather statistics and someday switch all to the most common MAC list).
Second, Nintendo may relay streetpass data between MACs, in that case you will get streetpass data from the other people, even from the real Nintendo Zone. It is unknown when or how Nintendo servers doing such relaying.
So if you're on Windows, have a 3DS with fw 9.3+ and have passed maccheck.cmd - nzone.exe is your only option.
It means that at least one dumb is spamming a MAC list with no delay, so you're getting his spotpass data twice and MiiPlazza won't show you twins