Early on in medical school, it would be wise to pay attention to the role imaging plays in your cases. Keep your mind open to the specialty and what it entails, as this will give you a taste of what happens in radiology without committing a lot of time.
Do some radiology electives, and try to spend time in different areas to get a good sense of what the resident and the radiologist do in their day. When watching the residents and the radiologists interpret films, ask good questions inbetween images.
Talk to radiology residents, and ask them what the training is like, what they like and dislike about their specialty and their program. Talk to radiologists, and ask them what they like and dislike about their job. Ask them what their day is like. Ask them if they have any regrets about their choice of career. Ask if they can give you any advice that they wish they had received when they were first starting out.