"When I'm trying to use my wireless network from either my kitchen or bedroom, the signal seems to be much weaker than in other parts of the house. What can I do to make my wireless Internet signal stronger in those parts of the house?"
Wireless networks are like most other radio waves in that things can cause interference and make the signal weaker in an uneven fashion. For instance, in your kitchen, it could be that the direct path for the wireless signal attempts to go directly through your heavily insulated refrigerator, which translates to massive signal dropout. Wires in the walls and the walls themselves all add to a dampening of the signal. There are a couple things you can do to make your wireless Internet signal stronger.
One thing you might look into is moving the location of your wireless router. If you have an available place in your house to put your network connection closer to the places you use it frequently, this is a good first step. Often network connection issues are related to the wireless access point or wireless router being at the opposite end of the house from the places where it is accessed. I realize you can't always relocate the connection due to the way the house is wired, but putting the access point in the center of the house usually makes it more accessible everywhere.
The next best option is to add a stronger antenna to the wireless access point. Wireless routers typically offer limited signal strength from the antenna included in the box. You can boost the signal buy buying a better antenna. These vary a bit by router manufacturer, but Amazon offers a great wireless antenna selection.
A third possibility is that the wireless antenna in your computer isn't strong enough to effectively pickup the signal. You can help address this problem by purchasing an external USB wireless adapter, which helps make sure the antenna isn't getting interference from any of the components inside your computer.