Instructions
Complete side quests. "Fallout 3" has a number of side quests that reward you with bonus items, special skills and, sometimes, bottle caps. Completing side quests also gives you more opportunities to complete the following steps.
Upgrade your "Barter" skill. By dumping skill points into "Barter," you'll save caps on items you purchase and make more caps on items you sell.
Upgrade your "Repair" skill and salvage lots of armor and weapons. The better you can repair these items, the more you can sell them for in the shops. This skill works well in tandem with "Barter" for the purpose of making caps.
Upgrade your "Speech" skill. When discussing rewards with other characters for taking on new side quests, you can use your "Speech" skill to demand a higher amount of caps for helping them out. The higher your "Speech" skill, the more likely you'll be to succeed in your negotiations.
Become a Slaver. Locate Paradise Falls, just northwest of Big Town, and, if you have Bad Karma, you'll be able to join the Slaver community. For every slave you send to Paradise Falls, you'll be rewarded with 200 caps.
Become a murdering thief. You should only do this if you've already got Bad Karma or you're really desperate for caps. Kill shop owners, roving traders, doctors, members of trading caravans and members of Rivet City Security. The first four always have caps and inventories that you can steal and sell elsewhere. Members of Rivet City Security are equipped with sub-machine guns and armor that can be sold for a lot of caps if you repair them.
Hunt Super Mutants. Normal Super Mutants and Super Mutant Brutes often carry Hunting Rifles and Super Mutant Masters usually carry Chinese Assault Rifles. Both of these weapons can be repaired and sold for a lot of caps. This is a good alternative to Step 6 if you want to keep a Good Karma rating.
Use the "Fortune Finder" perk. This perk is available to Level 6 players with a "Luck" value of five or more. With this perk, you'll find more caps when scavenging through desks, lockers, cabinets and other storage containers.