I think I regretted not doing more to develop my self-confidence and push myself beyond my comfort zone. In today's world, you will want to stay current on technology. You will learn to learn as you go. For example, if you are reviewing a company's time records, there's no way you can learn their system prior to that then!
Investigations can revolve around many things, so unless you already know which way you are headed, you will want to be exposed to as much as possible.
1. Math/science: How long did it take the driver to react and stop, with 6/32 tire tread depth on a road that was newly laid asphalt, that was wet - in the dark, with only moonlight for visibility, if he had a blood alcohol level of .02?
2. Science: Should a doctor have foreseen an adverse drug reaction when the patient was prescribed two different medications, both of which had a side effect of causing seizures? How does each medication work on the body?
3. Finance: How much is the company worth? Is the company following standard bookkeeping procedures or does something look strange? What are they doing, what are they hiding?
4. Basic sociology/psychology, understanding of diverse human cultures and subcultures, etc.
5. I don't know, but some understanding of how computers work, metadata, etc. There is a wealth of information on computers. People think they are clever and delete things, but, are they really deleted?
6. A class covering basic business organizational structures and business operations.
I always encourage people interested in law to take Logic. It is usually in the philosophy department. It is good. You will need to learn to think sequentially, to break things down into timelines, etc. Critical thinking is extremely important to your success.
Please use your electives wisely! Also, sometimes there are classes you can substitute for required classes, such as possibly taking Constitutional Law rather than US Government. Read through and find these substitutions!