Make it known from the first day of the semester that the classroom is a judgement free, ego-free space where everyone can safely explore ideas. You could even make it one of the 'class rules' --- I have several that I cover on the first day. I have had students remind fellow students of this ego-free mandate during the course of the semester. It sets a tone for collaboration from the onset.
Another method I use to 'set the tone' of the class is to play music before class starts. I play a random assortment of music from Pandora Radio, or music that shares a theme with the subject matter of the class, and/or ask the students for suggestions. I have noticed that when I play music before class it encourages friendly banter between students (as opposed to them sitting fixated on their phones or with earphones in etc.) Speaking of friendly banter - I always try and arrive well before class officially starts and talk informally with the students. If you know their interests and ambitions you can reference these in class as examples and scenarios.
I 'try' and limit my presentations to no more than 20 minutes; I say 'try' because sometimes this doesn't work. I like to talk. If I know I have a long presentation, I try and punctuate the presentation with questions and activities to break 'the lecture' into chunks.
I put class PowerPoint slides online for the students to download: that way they can focus on the class, activities, and conversation, rather than feverishly writing down every word from the slides. Needless to say, writing every word on the PowerPoint is not effective note-taking (see Cornell Note Taking and other solo activities) That is one of the reasons I have reduced the amount of words of my slides (if I use them at all!) Often my slides are just an image with no words --- the image primarily serves as a reminder of what I want to talk about.
If you ask a question and want the students to answer, pause longer for the answer than you expect --- tell the students you will wait.... (this is sometimes much longer than feels comfortable). I always tell the students that "I will wait"; I even had one student once say to me, after a rather lengthy uncomfortable silence in the class, "are you doing that 'wait' thingo?" Embrace the silence. Some students need time to formulate their responses in their heads or on paper before they will speak in a public setting. I have also heard that some professors will say " I will wait to until five hands are raised before we proceed." Pausing in class encourages students to think or reflect on the subject matter.
Don't let one or two students answer (dominate) all the questions --- quieter students will rely on the vocal ones to answer all the questions and they will stop trying. I was that student who was quick to answer and once a professor said to me "Catharina, let's let other students answer this one" - at first I was upset, but later I realized that hearing everyone's voice is important. I think I learned to be a better listener as a result.
Break the students into small groups for discussion.
In my experience, students who are facing one another, as opposed to looking at the back of each other's heads, are more likely to communicate. Try rearranging the seating (see Up and Moving!).
Another cool exercise introduced to me by Dr. John August at the Wakonse South Conference is Fortunately, Unfortunately. Dr August explains: "I usually talk about a topic in a mini-lecture, stop, and then ask the students these two questions in an alternating way. My students seemed to enjoy the exercise once they understood what I wanted from them. I was pleasantly surprised that they chose to share important concepts, rather than pieces of trivia."
And how do you stop them talking and regain control and silence in the room?
I have always used a variation of this methodology - but saw it really work in a very very large class setting at a teaching conference I attended. When you want the students to quieten down and regroup as a large class, raise you hand in the air. The students are instructed that when they see a raised hand they should raise their own hand... this works like a wave across the crowd and quickly quietens the room.