I am a first year teacher and understand your pain. My students talk a lot too.
One thing that is ineffective (at least with my kids) is yelling. It works sometimes, but if you do it all day, they eventually tune you out. Plus I noticed after a week or yelling, my throat started stinging and hurting. I was about to become hoarse.
So what I did, is I mentally pinpointed the "leaders" (kids who instigate trouble and talking) in my class and made an example out of one of them.
I told everyone to stop talking and I watched one of the leaders. The second he started chatting, I picked up his desk and moved him to the back of the room. I slammed the desk on the floor hard and said calmly, "I'm not playing around. You talked when I asked you to stop so this is your seat the rest of the day".
The class weren't perfect angels, but they acted a lot better.
Also, give your class leaders responsiblites in the class. I had a girl who constantly talked, played and lagged at the back of the line whenever we went out into the hall so she could look into other classrooms and stuff. So I made her this week's line leader. She now keeps the other kids in line when they talk or act a fool.I don't know if they have recess or not, but it could world work with any 'fun time that you might have during the day. I just say that I'm going to stop and wait and I start looking at the clock. However much time it takes them to get quiet, I take that time off of recess. I also do Fabulous Friday which is something that they earn. I would start by sending home a general note to the parents about the talking during lesson time and then tell the parents what the behavior reward is and what the consequences are. I also send home a weekly conduct slip where I tell them exactly what the problem is. My final resort is 'islands'. I had several student that simply could not work with a group and became an island. I tell them about this ahead of time and tell them that I have got to see that they are trying not to talk. Some students do better sitting alone anyway. My son was one that had trouble with a group. He always did better alone.You sound like a student all of us would love to have kurtis.
I teach 1st grade so they are really pretty clueless that you are even talking sometimes. I have started a system where I count down from 5 and time I am going to start something new. If students are still talking when I get to zero then I start implementing our disciple plan (I am sure whatever yours is will suffice). At the beginning of the year I also told students that the only time they may talk while I am teaching or giving instructions is if there is an emergency. Now whenever I am talking and someone else is talking (or interrupts, which was quite frequent) I just say "Oh, (child's name) do you have an emergency?" Of course they say no. Then I say "I would really like you to pay attention, because I want you to learn what everyone else is learning, and you cant do that if you are talking. Okay?" And they say "Okay"...thinking that they really missed something.
Now this is probably to "young" for your students, but they may feel childish if you talk to them this way...that or they will roll their eyes at you. Either way you can (and probably should) modify it a bit. But it seems to work wonders. I used it one day when the principal popped in and she loved the idea and complemented me on it.I am not a teacher, but I agree with IN14, I would make them share what is so intresting that they cannot wait until they are on there own time. Class time is YOUR timewow im glad ur not my teacher (im in 7th grade) HAHA