Just bear in mind that some things that were important in undergrad and not as important in med school. ECs for instance -- the only one that is going to have much impact for residencies is research. Basically residencies will focus on Step 1 score and clinical year evaluations/grades. The basic science grades and non-research ECs are so far down the list that they rarely come into play. However good basic science year grades tend to mean you are better prepared for Step 1.
I wouldn't focus much on specialties as a premed. The vast majority of folks change their mind at least once during med school, and you will often learn during rotations that something you thought was cool really isn't, and something you thought you wouldn't like is kind of fun. So go to med school with an open mind. Bear in mind that for something like derm, because it is so competitive (there aren't a lot of spots, it's high pay and cushy hours, so lots of people want it) your board scores and grades can shut you out of the running long before the match. So I probably wouldn't recommend going into medicine if you can only see yourself doing this. So too rads. It's great to have lofty targets, but most folks end up in the patient contact intensive specialties (because that is where the bulk of the spots are), so if that doesn't appeal to you, you actually may want to think long and hard about med school. Only 5% can be in the top 5%. Nobody bets on those odds.