What is the best way to increase the range on my WIFI router??

Somethign about range boosters.. Your wifi connection is only as good as the least powerfull device you are using (IE laptop/PC or Access point). This means putting a range extender on just the AP will not extend your range if you client machine has a low power interface. Try turning down the speed of the wireless connection. the lower the speed the farther it will shoot (including through walls). Also wireless B goes through walls better than wireless G so you may be able to mess with that on your router as well. After that maybe better antennas on both of the devices. try http://hyperlinktech.com to see some stuff that is available for wireless.

A signal booster is the best way. They aren't very expensive. Go to Best Buy or Circuit City.

depends on your router. Most have a replacable antenna. If it doesn't a signal booster is your next best bet, check pricegrabber for a good one (http://www.pricegrabber.com/).

Some brands offer antennas, or signal boosters. You can look for one online: This is a very good store: http://www.outpost.com

The "best" way is to run wire and add another wired access point in another part of the house. Beware of range extenders, because every wireless repeater you add to your WLAN will generally reduce the performance by 50%. If you don't want to add another wired AP, try using a high gain antenna set but keep your receipt... Sometimes they make things worse, because the signal radiation pattern on a high gain is more flattened out, shaped more like a pancake, instead of the standard donut shape. In a 2 or 3-story home this higher gain can actually make things worse. Also, make sure you place the access point(s) in the best locations out in the open, not between a pair of metal filing cabinets for example. Keep the antennas in a vertical orientation, this stuff is all vertically polarized. Finally, make sure to eliminate sources of interference like 2.4GHz cordless phones, etc. Change channels too, choose from 1, 6 or 11 if you have a neighbor who might be using the same channel as you.

Two-storey buildings and older houses have always been a problem for WiFi performance.... usually because of metal mesh reinforcing used in the wall and floors. The simple solution is to run a cable between floors and add a "Wireless access point" on the upper floor. There are also "repeaters" available which make use of the house wiring as a connection, but I'm a little wary of that idea... If neither of those appeals, you might take a look at the newer networking hardware, compliant with the 801.11N draft spec... sometimes called the "Pre-N" spec. These seem to be better at working in marginal and difficult conditions, being better at handling the reflections and multiple signal paths that older buildings tend to create.