Note: This trick requires you take the "evil" path. After agreeing to help Mr. 
Burke nuke Megaton, go into every single house and steal everything (any little 
piece of junk you can carry). Sell them to the local shops (Craterside Supplies, 
The Restaurant, Moriarty's Saloon, etc.). If a particular house is locked or you 
need a key to get into a safe or something of that nature, just kill the owner 
of the property, and get the key from his or her body. Kill everyone in sight, 
especially the shop owners because you can get access to their entire inventory, 
plus the Caps that you have already spent on them. Kill every one and collect 
everything to leave Megaton empty. You should have at least 600 caps. Remember 
to sell some of the things you gather to the shop owners because you cannot fast 
travel when over encumbered. This can be done in almost any town you visit. To 
avoid getting over encumbered, get all the supplies that you can possibly carry, 
then drop the rest just outside of Megaton. Fast travel to Rivet City or some 
other marketplace. Sell what you have, then return to Megaton, and repeat the 
process.

In the "Strictly Business" quest, capture Susan Lancaster, and get your reward 
for her capture. Afterwards, speak with her in the slave quarters part of 
Paradise Falls. Note: You will need one of the slaver's keys to access the 
slaves quarters; pickpocket one. After entering the slave quarter's, speak with 
Susan. When she asks for help, choose the option "You're a slave. Deal with 
it.", then return to Grouse to collect the reward again. Grouse will think that 
you captured her again. You can repeat this as many times as desired to get 250 
Caps and a slave collar each time.
Save all pre-war books you found (not scorched or ruined). Go to the Arlington 
library. At the southeastern corner, you can find an NPC that will buy those 
books for 100 Caps each. You will also get 10 experience points for each book 
you sold.

Do the "Riley's Rangers" side quest. After rescuing Riley and escorting her back 
to her base, she will ask if you want to help her out by mapping the area, and 
she will pay you. Do not tell her that you will help her just yet. After 
reaching level 20, use the "Explorer" Perk. Once you have revealed every 
location on the map, go back to her, and tell her that you will help her out. 
Then, tell her you have got some new locations for her. Depending on whether or 
not you have already done it, you can make upwards of 2,200 Caps.
Easy Hacking, Speech, and Stealing bonuses 
Save the game before starting a dialogue with a Speech bonus, hacking a 
computer, lock picking, or pick pocketing. Then, simply reload the game if you 
fail the challenge.