Aside from conventional tips like fashion and stuff, having good quality friends who let you finish your sentences but speak for your good character behind your back goes a long way. Since you'd disclose your speech impediment early, also disclose any secondary behavior that may look like non-verbal communication but it's not. For example, looking away can be either a secondar behavior or a "I'm looking at something else" signal. Sudden loud speaking is either a secondary behavior or a "I'm angry" signal. If you have any of them as secondary behaviors, you should disclose them so you are not misunderstood.