1.To convert a casual way "だけど" into a formal way should be "ですけど". Meaning is "but" and you can use it when you want to connect a sentence to another. ex: えいがに　いくんですけど、あなたも　きますか？ (we are going to catch a flick, but do you want to come with us?) 2. To expect the listener to say something after that. ex: A: のどが　かわいたんですけど..... (I'm thirsty.....) B: きっさてんに　いきましょうか？ (Do you want to stop by a coffee shop?) 3. When you are not sure exactly what you should do or what you should say next, and want to make it vague. ex: まぁ、それでも　いいですけど..... (Well, that's fine for me though.....) Nowadays, Japanese people tend to add "だけど" or "ですけど" at the end of the sentence, but actually there is no such a big meaning.