Here’s how you can block unwanted contacts in Google Talk and also prevent Gmail from auto-adding them to your chat list in the future. 1. Login to your Gmail. You should see your Google Talk account on the left. 2. Hover your mouse pointer to the contact that you want to block. On the popup that appears, click on the “Video and & More” button. Select “Block”. (Sorry Josh, I am not really blocking you. It is just for illustration purpose) That’s it. You have successfully blocked the unwanted contact. Next go to the Settings option (at the top right hand corner). Click on the “Chat” option. In the “Auto-add suggested contacts” section, select the option “Only allow people that I’ve explicitly approved to chat with me and see when I’m online”.
Save the Settings. That’s all you need to do.