Fallout 4: 10 Things We Learned in 10 Days

Scavenge As Much Ammo as You Can

Two quick thoughts about ammo in Fallout 4. 

One, I highly recommend carrying a variety of ammo around with you at all times. If you find ammo, loot it. You can never have too much ammo. On several occasions I've run out of the good stuff or ammo that's applicable to the situation and that has lead to near death experiences. 

And two, never ever sell or fail to loot ammo for the powerful weapons. Mini Nukes aren't as common as pistol ammo. Ammo for the awesome weapons is typically a lot harder to find. Horde it. And then store it for when you need it. And you will.