Basically speaking, biomedical engineers need to have additional knowledge and eventual expertise in biology, biochemistry and physiology. It helps to know computers -- as with all engineers -- but also electronics. Biomedical engineers are essentially mechanical engineers with additional knowledge of the human body. I assume you're only talking about human biomedicine. The thing I would recommend is to contact a counselor at a school that produces biomedical engineers and ask for a required course list. This will give you excellent insight into the different requirements. I would also, as usual, seek out biomedical engineers who are currently working and ask. This is a pretty logical step that many students simply don't try. Now, as with all engineers, you'll find quite a range of actual activities and projects. Just as medicine branches out wildly in terms of specialties, engineering does as well. I personally have been extremely fortunate to have worked on a wide range of projects, and this has given me a lot of very enjoyable experience. However, that is not the rule. Some engineers have focused on one particular job or specialty. So I would recommend talking to as many people as you can find to give you advice. You'll also find this pretty enjoyable.