TL:DR To get picked you need:
[1] Silk Dress - Tell dress maker you want "Soft" & "Shimmers"
[2] Blonde Wig - Beat the guy in gym at Squats
[3] Sexy Cologne - Get "digestive" medicine and give it to toilet user in pub
[4] Diamond Tiara - Buy 200 Gil item from vending machine for shop owner
[5] Lingerie or
Bikini Bottoms - Obtained in the Honey Bee Inn left hand rooms
[6] Make Up - Applied in Honey Bee Inn after getting underwear.
To be chosen by Don Corneo, you will need the best items possible. I have read that even with the perfect set of item, sometimes you will still not get chosen. So make sure you have a back up save before going to see him.
He is located in Wall Market in sector 6. You go here early in the game. You are trying to find Tifa and whilst sitting in a park, she will go past you on a carriage. You follow her in to Wall Market. When you enter, head off the screen to the right and talk to the people in this area. One of them will tell you where Tifa is. You can then go back to the previous screen and head north until you find the bouncer. This starts the quest of crossdressing.
[1] The first task is to get a Dress. The dress maker is the top left of the first area, enter and you will be asked to go to the pub to find the dress maker. Leave the shop, go north one screen and the pub is on the left. The guy is next to the door. When he asks you how you want your dress, you should respond:
"Soft" & "Shimmers"
This will net you a
Silk Dress. Now go back to the dress shop and try on the dress.
[2] You will be tasked with getting a wig. (Make a save before progressing. If you fail at the squats, you can reload to try again). Head north and on the right of the next area is the gym. You have to talk to the woman to start the squat match. You just need to press
, then
, then
and repeat. Make sure the previous animation has finished, before pressing the next button. It isn't too difficult as the other guy messes up a lot. As long as you don't make mistakes or take too long, you should get it. Winning gets you the
Blonde WigAt this point, you need to obtain optional items. If you go back to the dress shop then you can end up continuing the story and locking yourself out of the story.
[3] Next go the Diner which is in the top middle of the first area. Order any meal and when asked how it was, state:
"It was alright"
This will get you coupon for the pharmacy. The pharmacy is the building below the diner. It has a cat thing outside. Give the coupon to the pharmacist and get the
Digestive medicine. Take this to the pub from before and at the back of that is a toilet. Talk to the person in the toilet to give them the medicine and obtain the
Sexy Cologne.
[4] Now go to the top right of the first area and the guy in this shop will ask you to get him something from the vending machine in the inn. The inn is the lower left of the first area. Go there and stay for the night. You will then use the vending machine. Buy the most expensive thing for 200 gil. Take it back to the guy in the top right and he will give you a
Diamond Tiara.
[5] Now go to the bottom right of the first area and talk to the guy wondering around. He will give you a
Membership Card. You can use this in the area to the right. It allows you access to the private club. Go in to the room in either the top left (
Lingerie) or bottom left (
Bikini Bottoms), after the scene happens, talk to the bee woman to get the item. From what I read, you can get either of these, it doesn't matter.
[6] Now go in to the middle top room and talk to the bee woman on the left. She will apply make up.
You are now done, go to the dress shop to change (then make a back up save) and go to the Dons mansion. When in there, go up stairs and to the left to find Tifa. You will have a conversation and then be told to go see the Don. Leave the room and you will go in to see him and he will pick who he wants. If he picks Cloud then the trophy should unlock when you enter his room. If he doesn't pick Cloud then quit and load the game to try again (he picked me first try so I don't know of any tricks to make him pick you if he doesn't).