Tactics refers to the methods used to achieve goals. Tactics can range from totally threatening to wholly inducing, and usually actors should use a wide variety to create believable interactions. If an actor has, for instance, the goal "to threaten" then various tactics might be used to threaten.
Atticus is ready to speak the truth,Sheriff Tate convinces Atticus that it is in nobody's interest to tell the whole truth when it comes to this particular case. Everyone will lose if the truth came out.