There are a few requirements for recieving Perfect Town status.
Ask Pelly or Phyllis about the environment for tips.
In general, the requirements are:
Pluck all of the weeds from the ground
Do not leave trash (boots, cans, tires) on the ground.
Do not leave ANY items on the ground
(clothing, furniture, wallpaper/flooring, stationery, fruit)
Lots of flowers - 3 or 4 in each "acre"
(although the "acre" business is a rumor that has not yet been proven or disproved)
So just plant flowers all over the place.
If they wither, water them instead of plucking them away.
With trees, spacing is key.
Having too many trees clustered together will lead to
Pelly/Phyllis saying that you have too many trees in the town.
However, if you remove a tree, they may say that now you don't have enough trees.
Try to have 12-14 trees per acre
(assuming that Wild World does, indeed, utilizes acres).
The Perfect Town Guide on gamefaqs.com says that all eight neighbors
must be present in order to maintain a Perfect Town.
This is not true.
Your town can contain any number of residents in order to be Perfect.
After a few days of having your Perfect rating
(Pelly/Phyllis will say that the town is "a great place to be"),
a rare and beautiful flower, the Jacob's Ladder, will begin to pop up around town.
I'm not sure on this, but I think that placing a Jacob's Ladder in your house qualifies as a Lucky Item.
In any case, they are pretty flowers and it's nice to have them around.
Also, after a full week of a Perfect rating, Pelly/Phyllis will reward you with a Golden Watering Can!
And finally - Happy birthday.