There are a list of things you want to keep in mind:
- Format
Choose FBX or OBJ to export from Blender to Unity, FBX is more complex, have more info, including different animations stages for example, i recommend FBX, but obj works too
- Modeling
You should do it in a way that you have less objects, geometry, everything well parented, etc, so low poly, join meshes, and VERY IMPORTANT: Check scales, try to aproach to real scales, AND the origin points and Axis are not the same for Blender and/or Unity
3.Animating

There is an Action Editor (Inside Dope Sheet Editor Type), this should be your main area when you are working on different animations, create a new, put the name, for example "jump", animate all the loop, and then create another, for example "crouch" and the same for all the animations
- Export Settings

(DON`T follow the settings on the screenshot, you need to tweak for your best preset)
This is the last field from blender to unity, but the most important point. You are going to have to tweak it until you get your perfect preset and then export all the meshes, but in the export settings of fbx you will need to have Selected Objects, the trasnform forward axis, geometry checks, apply modifers, and in your case, dont forget the animation tab in the export settings, where for example the check of "all actions" is what you need to heck to have all separated animations when import to Unity
Hope this help to have a better view of all process ;)