There is no normal. Some couples have their names picked for years, some wait until the 20-week scan when they'll probably learn the sex, and some bring the baby home before they really start to debate what to call him/her.
Whenever you feel good about debating it is perfectly okay. I think there are some laws in most countries on when you have to pick a name (like, first few months of the baby's life or something), but that's it.