Storing equipment and doing repairs
One of the most important things about difficulty level of "Fallout 3" is that your gear loses its durability during the course of the game. You can observe the changes in the state of your items directly from the Pip-Boy menu, but it gets even harder when you want to do something about it. You can't ignore this problem, because items in bad state offer bad profits from having and using them. This is especially crucial when it comes to weaponry, because you can lose a lot of damage points and a result you have to focus more attention on scoring perfect shots to nullify the difference.
Each time your equipment has deteriorated you must make a decision how to solve this problem. The most obvious solution is to invest points in development of the Repair skill. Sadly there are a few things you must remember about. The scale of repairs that can be done correlate to advancement of your skill, so you won't be able to bring back the original state of your gear at first. Also, you must have a spear item of the same type in your inventory to make the repairs possible. A much easier solution to the durability problem is to ask one of the merchants to make necessary adjustments. This is often expensive and the merchants will probably stop at 50-55% durability, so you can't rely on their skills entirely and eventually you should start spending points on Repair.
Most of the items in your inventory have a certain weight value, especially when we're talking about weapons and armor. You can't carry too many items, because your character won't be able to run or even move. The maximum limit isn't a strict one, especially since ammunition doesn't weigh a thing. Nevertheless, you will often have to find a compromise. A good idea is to hand over items to your team members and I'm sure that you've discovered this possibility on your own if you remember previous "Fallout" games. You should also store less important items in your house in Megaton or in your apartment in Tenpenny Tower. I would recommend that you visit merchants often and sell them unwanted goods. Make sure not to visit only one person, because it'll take some time for the merchants to gather enough bottle caps to be able to buy your gear. If you're desperate, try buying something for them, instead of just taking the caps.