The main tip for which choice will get you the boy you want is right in the gallery screen. When you select a choice that will boost your chances of getting a route, the choice will flash the same colour as the character's background colour on the gallery.

Therefore,

• Black = Limbo
  
• Blue = Shu
  
• Pink = Helvetica
  
• Yellow = Mozu
  
• Green = Scarecrow.

As far as I know, choices that do not show a particular colour when you select them do not have an effect on which character you will get, so pick whatever you like from those!

These are the only options I have found so far in chapter 1 that will affect which character's route you get:

• When speaking to Helvetica for the first time, if you select "I thought you were kind of annoying" this increases the likelihood of getting Shu's route.
  
• When asked if you are doing the article for just money or the scoop, selecting "Honestly, I need the money" increases the likelihood of getting Helvetica's route, whereas selecting "Forget the money, I want a scoop" increases the likelihood of getting Mozu's route.

Without getting into spoilers, most of what determines which character's route you get is done in chapter 2, by answering a series of 10 Yes or No questions. Here is simply which choices will make you more likely to get the character you want :)

1. Yes = Limbo, No = Scarecrow
   
2. Yes = Helvetica, No = Limbo
   
3. Yes = Scarecrow, No = Mozu
   
4. Yes = Mozu, No = Helvetica
   
5. Yes = Shu, No = Limbo
   
6. Yes = Scarecrow, No = Shu
   
7. Yes = Mozu, No = Helvetica
   
8. Yes = Mozu, No = Shu
   
9. Yes = Limbo, No = Helvetica
   
10. Yes = Scarecrow, No = Shu

Before the ten questions, there is also an option to select "You're sweet" when talking to Scarecrow. This will make you more likely to get his route (thanks to user RusCSI for pointing this out, I forgot to add it!)