What can it cost?
The more elaborate showers can cost up to $2000 to stage for 30-40 people, but that includes everything from invitations to venue hire and full catering.
The most involved shower Johnson organised was a "nautical" sailor-themed party for a baby boy, with co-ordinated cupcakes, games, invitation, food labels, decorations, outdoor seating, photography and gift bags for guests.
"I ended up doing the whole guest list.
"That was the full package."
Planners cost about $55 an hour, plus a $200 refundable bond. But it's usually catering that ends up accounting for most of the bill, she says.
What's an appropriate gift?
Gifts can vary, but Mrs Johnson suggests a register or everyone chipping in to get a bigger gift.
"A lot of people set up a register at Nature Baby, which is more of an expensive store, but also Baby City."
Mums-to-be then choose everything they want their guests to buy, Johnson says.
"When you've 40 friends it's very easy for people to get the same presents."
Common double-ups included lotions and baby clothes.
"You end up with too much.
"Another really good way to do it is everyone going in together and getting a really good-sized present like a car seat."
Planners also give advice on how to keep the cost of a baby shower down.
"There are so many different ways you can do things, especially with decorations which are really cost-effective."
When is the best time?
Showers, which are generally thrown by friends of the expecting mother, are always done before the baby is born, but not so late that the mum is uncomfortable or there's a risk of her going into labour.
"Once all the complications-side of being pregnant's passed, it's either in their late 20s or early 30 weeks' pregnant when they have the shower because they're still feeling and looking pretty good as well," Johnson says.
Who's invited?
The Yellow "How To" Guide says most baby showers are girls-only affairs and along with female relatives such as sisters, mothers, aunts and grandmothers, female workmates, close friends, friends from exercise and ante-natal classes can be invited.
However, these days it is not unusual for the father of the baby and a few close male friends to be invited, too.
The diversity of the group often means not everyone will know each other.
"Having a few party games arranged for guests to play gives structure to the party and helps everyone integrate and get to know each other," Yellow recommends.
"Games are excellent, too, to add a spark of life when the party seems to be flagging," it says.
Cost cutting tips
-Use e-invitations
-Set up a Pinterest site to generate DIY ideas for the party
-Do the cooking/baking yourself
-Picking flowers from the garden will "spruce up" the event
-Ask guests to bring a plate
Source: Centre of Attention
Gift ideas
-Cotton "baby wraps" from the Sleep Store $24.95
-Baby timer $38
-Towel bib $6.95
-Nature Baby portable baby basket $59.95
-Baby suit $20
Source: Kidspot