Make your Playmate follow you to some sports equipment. Tell your playmate to "Use".
Repeat this several times and eventually they will get high Physique. This works with every other peson in the game as well.
When taking a picture for a photo shoot try take one when the model winks. This will give you more stars for the shoot.
Now gain a certain amount of points, say about 30 & save the game. Wich will take only a short time. Now if you want to checkout all the unlockables at right now, with around 30 points you will be able to unlock about 4 at once. Once you have unlocked & tested the cheats or viewed the playmate pictures, reload the game & test out more! Keep doing this untill you have seen & tested every cheat in the game!