What is a good way to earn caps? I have always seen NPC's with stuff, but they dont have much caps and I dont sell stuff to them! What is an another way to earn money?
In the few days I've been playing, I've learned this: Pretty much everyone (on their barter alts, anyway) keeps large quantities of poor-quality ammunition and weapons on hand. Almost as soon as NPCs regenerate their caps, players sell the crap and get caps for it. Basically, you have to be extremely lucky with your timing. Within 1-15 minutes (depending on location), the caps will be gone.
You'll have better luck in out-of-the-way places like San Francisco or an unguarded town, but even San Francisco is cleaned out on caps most of the time, in my experience. In an unguarded town, 90% of the time you'll be killed and have your items taken, so even if there are caps available at traders there, there's an excellent chance you'll lose them before (or right after) you get them.
As for making caps from players, no one buys poor-quality ammunition or weapons. They'll only buy ammo and weapons that require HQ ores and minerals, and to get these, you'll have to risk mining at an unguarded mine... or join a gang... or strike a deal with an existing gang for "protection," perhaps, so they won't kill you when you mine at a dangerous location.
Fortunately, other than cars, mines and bases, you really only need caps for professions and train tickets (AFAIK). Even so, I find this system of caps distribution incredibly random and aggravating.
Instead of regenerating 10,000-30,000 caps every few hours (or whatever it is now), I personally believe it should be something like 1,000 caps every few minutes.