I disagree with another poster that the core of DM encouragement is rail roading. Nor do I agree "strait forward" mysteries are railing the party. But this might be a disagreement in terminology.

"Rule of three" clues, context clues for the scenario and the diamond method are the best tools to subtly hint to the party in the direction of non confrontation.

To go further

Rule of Three: Rule of Three is putting three clues in the start of the mystery. These are used to drive the direction of the mystery and can give wildly different options for tackling.

Context Clues: Mention to the party the mayors grip on the town, possibly the ignorance of the guard. If a lawful party the party won't murder hobo if you establish that even with the truth, a coup will be frowned upon.

Diamond Mysteries. Diamond Mysteries are shaped like a diamond, meaning they spread out with many clues leading to the same outcome.

In the end as long as you don't push the party to do x and let them do y you should be good. I recommend Seths "Run the Game: Mysteries" the Alexandrian running mysteries and the Gunshoe System to get afew ideas.