txt file that comes with the mod files, etc.) - heed their advice above all else. Most mod creators will include some form of 'Installation Instructions' text (either in a description on the site/service you download the mod from, or as a separate.
So, with that said, I can think of 3 major things to consider when trying to determine load order: I use Nexus Mod Manager, and that's what I've based my answer on - if you use another tool, YMMV. Check out their documentation for how that all works. Depending on which one you use, there will be prompts or features that help you work with mod conflicts and load priorities.
FO4 has some build-in mod support OOTB, but there are a lot of tools out there on the internets that make modding much easier, especially if you want to run a heavily modded game. First off, you will probably want to use a separate mod organizer program of some kind.
