Dead Rising

If you only want this achievement (because you somehow missed the chance to get 8 female survivors):

The easiest way possible to obtain this one is on day 2. Wait until you get the scoop "Above the Law". You end up in Wonderland Plaza. Entering from Food Plaza you will see two survivors hanging above a bunch of zombies ready to eat the survivors. Kill all zombies (queen in a jar does the job fast!)

Have something to throw like an apple or something light so they fall down from the pink bunny. Damaging them too much will cause them to defect and become hostile and they will die (because they will try to kill you!)
Let them join you. Fight Jo the cop, beat her. If done right, you will have 6 survivors. (2 survivors from the bunny, 4 from the store.)
Use the secret passage to Paradise Mall, go to Entrance mall.
Fight off the three snipers, you will find Wayne in the cosmetic store.
At the same time, also in Entrance plaza, go to the antique store and pick up (after a long dialogue and some convincing from Frank!) Floyd.
(Who you might need when you go for the Transmissionairy achievement, as he needs a bottle of wine at some moment in the game to ease the tension)

After Floyd joins you, the achievement should pop.

*** start a new game in 72-hour mode and kill all survivors you encounter - this is important ... don't forget to kill Cliff's 3 captives in the room next to Crislip's. if you don't kill them all, Nick and Sally won't spawn at the appropriate time on Day 2 which means you won't be able to get the achievement ***

as has already been noted, this YouTube video is great:
Day 2 @ 11:00am in Leisure Park

- be in Leisure Park waiting on Otis to call re: the Restaurant Man scoop
- take the call and head into Paradise Plaza; kill Ronald [RESTAURANT MAN] in Jill's Sandwiches
- use a queen to save Pamela in Paradise Plaza
- After Pamela starts following you, talk to Heather in the toy store and give her a weapon
- Escort Heather and Pamela to the bathroom where the Wonderland Plaza shortcut is
- Wait here until noon when you receive the "Above the Law" scoop
- Continue waiting until 1:00pm in the Paradise Plaza bathrooms with Heather and Pamela
- At 1:05pm take the shortcut through to Wonderland Plaza
- Give Heather and Pamela a waypoint in the bathroom right away
- Go kill Nick and save Sally who are hanging from the bunny in Wonderland Plaza
- Escort Sally back to the bathroom waypoint by holding her hand (this is easiest)
- Go kill Jo the cop
- Right after killing Jo, leave the 4 captive women tied up and go quickly down to the bathroom to reset the waypoint for Heather, Pamela, and Sally
- Head back up to where Jo was, untie the 4 women there and escort them to the bathrooms - you have to nudge them or hold their hands one at a time - it's annoying but don't press "Y" otherwise your waypoint will be reset which you don't want
- When all 7 women are in the bathroom take the shortcut to Paradise Plaza
- After the Sean/cult cut scene, quickly run back to reset the bathroom waypoint for the 7 women so they don't get mobbed
- Head back and kill all of the cultists, then save Jennifer who is in the box
- Achievement should unlock as soon as Jennifer joins you

Tour Guide

If you wan't to hit 2 birds with 1 stone you can obtain this achievement and the Frank the pimp achievement (escort 8 female survivors at once) by following the video I found on youtube done by PJtheplayer:


I do recommend having the Mega-man blaster which you obtain by killing 53,594 zombies.