Wireless Broadband Tips

I've been using a Linksys hard-wired router for over 2 years without any
problems.
7 or so months ago I added a WAP to one of the router's ports so I could
also have
wireless internet on my notebook.
It works pretty good with me being able to travel 70 feet before I lose any
signal. Not to mention
it's traveling through appx. 6 walls to get to me.
Today I ordered an instaly Linksys Wireless USB Adapter for my pc I just
built out of scrap parts
for the garage room.
The total distance from the WAP and this wireless usb adapater is appx. 150
feet.
Before it arrives in a few days I was just curious to know if anyone has
tips for increasing / optimizing
my wireless range.
If anyone has any tips please let me know!
I've heard you can buy antenna amplifiers but have no experience regarding
this.
Thanks.
Btw, I lock the wireless to MAC Addresses, use WEP, and shut off
broadcasting of the SSID.
It's better to be safe than sorry.