For me, there are no difference between でも and けど. Both of them mean "but". Also both are casual words. Yet if I was to say it, でも is used in the start of the sentence (like I used Yet in this sentence). Otherwise けど could be used in the middle of the sentence, or connected to other words. For example, 「私は朝起きたけど、〜」(I woke up in the morning but〜) In this case, you cannot say 「私は朝起きたでも、〜」 If you want to, you have to cut the sentence like 「私は朝起きた。でも、〜」 I hope my answer would help you...