When you're not a Christian yourself? Just got snapped at on FB for asking this of a girl on a forum who asked how she'd go about getting her baby Christened...
My point was - if you're a practising Christian ask at your local church - if you're not, why do it? (Phrased slightly more delicately)
I can't see why people do this - they don't randomly take their kids to mosques or synagogues asking to sign their kids up to other religions they don't follow themselves...
Is it just for a party?