Gain a lot of currency and then save the game. Afterwards, talk to the Major who gives you hints. You should get 150 currency to get all three hints. After you have heard these helpful hints, load from the last save point and use the info to help you on your objective. If you keep the same amount of currency, you can do this for the next objective. As you have used the hints but not saved afterwards, at the end of the level the game will not register their use, and you can get a higher grade.