The game is designed to make you lose. Losing is more interesting, I think, when it is not on purpose, and winning is more rewarding when you have overcome a challenge (even if only through meta-knowledge of how the game works). That being said, it seems like I've made the game a tad too loss-oriented.

So, for those who are unable to get to the good ending, I have listed a fistful of options that should guarantee you a fortunate fate. You don't have to choose all of these options (for example, you can act all cutesy with Manou throughout the game and still get to the good end), and I've glossed over other decisions that also have consequences; but I think that even if you deliberately choose the worst of all possible courses of action, as long as you follow these instructions, you should be fine.

BEWARE! Tons of spoilers below.

During the introduction, when and if you can, choose:
- "Enough for a few drinks."
- "I fucked her, didn't I?"
- "I hope to get myself some fresh meat in this tavern!" or "Ignore her"
- "I don't give a damn about them."
- "Slap her big ass"

If you have chosen enough of the previous options (4 or 5, maybe 3 in some cases), challenge Natacha's gaze; otherwise, ignore her (or just talk to her).
If you challenge her gaze or talk to her, refuse to go buy drinks.

After that, it is wise to follow these little guidelines:
- You are not afraid of Natacha! No, sir.
- Your tastes AREN'T towards surface operations, you like to destroy dungeons, like a real man!
- You are also a man of boundless munificence.
- Choose "The first signs of ruin are rarely visible on the surface."
- Do not choose "I'm sorry, it's not my fault. She made me do it."
- Contemplate Natacha's bosom as much as you can.
- Choose "To be honest, that quite how you looked to me when we first enter here."
- Choose "Did he thank you for your service?"
- When Manou asks for a drink, just get up and go or choose "Henri seems to me to be this kind of obedient lad."
- Buy deluxe drinks
- Choose "No one wants to hear about the disgraceful things I have mercilessly inflicted on my fallen foes."
- To give you courage in hard times (the arm wrestling bout and the bar fight), meditate more on Natacha's attributes (if you can) than on Manou's ones.
- If you find yourself alone with Natacha, grope her. It goes without saying.

Finally, when the opportunity arises, immediately slide your hand down Natacha's shirt (and don't back down). Drinking more is not a good idea at times like this. Before the fight, say that you're just going to destroy him and his girlfriend's honour.

That should be it. Good luck out there. Maybe one last remark, the "victory scene" with Natacha comes in two flavors. It can be quite implicit (if you take her to your room) or much more explicit (if you don't). Have fun!