How can I make NetworkManager ignore my wireless card?

According to Gnome Wiki, the syntax in /etc/NetworkManager/NetworkManager.conf (in older versions it was /etc/NetworkManager/nm-system-settings.conf) is different than what I'd read Arch Linux Wiki. It should be:

[main]
plugins=ifupdown,keyfile

[ifupdown]
managed=false

[keyfile]
unmanaged-devices=mac:00:19:e0:57:86:af

This configuration makes NetworkManager oblivious to the existence of my wireless card, but still allows me to control it using other methods.

I think the wrong line may be:

unmanaged-devices=/org/freedesktop/Hal/devices/net_00_19_e0_57_86_af

as I didn't found that format specified in the official documentation.

Valid formats are unmanaged-devices=mac:<hwaddr> or, in recent Network Manager versions, unmanaged-devices=interface-name:<ifname>. Both are accepted together separated by semicolons, for example:

unmanaged-devices=mac:00:22:68:1c:59:b1;mac:00:1E:65:30:D1:C4;interface-name:eth2

This is an extract from NetworkManager.conf manual:

unmanaged-devices

Set devices that should be ignored by NetworkManager when using the keyfile plugin. Devices are specified in the following format:

mac: or interface-name:. Here hwaddr is the MAC address of the device to be ignored, in hex-digits-and-colons notation. ifname is the interface name of the ignored device.

Multiple entries are separated with semicolons. No spaces are allowed in the value.

Example:

unmanaged-devices=interface-name:em4

unmanaged-devices=mac:00:22:68:1c:59:b1;mac:00:1E:65:30:D1:C4;interface-name:eth2

Use the following /etc/NetworkManager/nm-system-settings.conf:

[main]
plugins=ifupdown,keyfile

[ifupdown]
managed=false

This way your interfaces from /etc/network/interfaces will be unmanaged by Network Manager, i.e. it will not try to do anything with them.