Does anyone have tips for optimizing a wireless internet connection?

I just moved in with a sibling and her broadband connection is hooked to a Linksys wireless router. After using this thing for a few hours, I’m already missing a wired internet connection. I’d appreciate any ideas that might give this thing some more juice.

I use a MacBook Pro with Mac OS X 10.5.6. I also have a PC desktop with Windows XP. The router we have is a Linksys Wireless-G Router with “Speed Booster” (LOL) or WRT54GS.