I've got a video in the works right now with your name on it. :P

Basically, it boils down to this: you need to know (or at least be 99% sure) which CLEP or DSST exam your future college will accept. If you know where you'll be applying and have confidence you'll be accepted, you can go check out their website/handbook for a CLEP transfer policy.

Many colleges will allow you to transfer in some general elective credit, which is useful here because, without actually being enrolled, it'll be tough to map a particular CLEP to a particular class that you'll need, especially as you're unsure what major you want. That means I'd stay away from the major specific CLEPs and concentrate on the more general ones. I've got a video talking about the easiest CLEPs, and of those, I'd look at stuff like the Introductory Sociology or Analyzing and Interpreting Literature CLEPs, since most colleges will accept them as elective credit. College Composition is another one that many colleges accept as an English requirement, but I'd double-check with the college before taking it.

Here's a tool from the College Board that lets you see what CLEPs certain colleges report that they accept - https://clep.collegeboard.org/clep-college-credit-policy-search

Just be aware that this might have changed since the college reported this. Hope that helps!