How to mingle easily with co-workers and start discussions?

Smile is a key to open any discussion as well greeting

Greetings first- saying "Hello, How are you? How are you doing?  that is all to start. However, you need to select proper timing and mood of your co-worker. 

Be soft spoken, cooperative, helpful and part of solution then every wants to enter in your circle beside you try to be part of them!

By saying greeting and start talking on common issues or interet. Listen carefully

lower your profile and speak on no bride

think you for invitation

  smile and greeting after we talk about the  work

Thanks 

Good answer which given by Mr. Fazlur, i agree with him 

Try to find common interests. 

Thanks for the invitation. I agree with the replies here!

Thank you for your invitation

Each greeting for all the interest and useful answers

Thanks for the invitation. I agree with the given answers from the experts.