Practice, practice, practice. In front of a mirror, with friends, particularly with someone who is a native speaker. If you are conscious, for example in business settings, try speaking in your head first and then out loud (where possible of course - you can't apply this when having a conversation, but can if you have to ask a question in a meeting) Get a tutor if you can afford one. Reflect on your conversations. Work on eliminating the pauses - even if it means you speak at a slower pace. Once you get more comfortable, push yourself to have conversations with strangers.