Edwin,
For wireless routers/AP moving them around to find the right location is pretty normal stuff. Since in the main you are going to be taking advantage of multipath (the signal is bouncing around, the the antenna is hearing the same thing from all sorts of directions and timings) the notion of fiddling with the physical location of the router makes sense.
Office settings are usually easier than residential sites. But a first step is to use NetStumbler on a laptop so that you have some sort of measurements to compare any changes you make.
Second step is to physicly move the router/AP around. I have one site that if I move the WRT54G one inch to the left horizontally, and 1.5 inches verticly, my longest shot goes for "poor" to very good. Go figure. I took a small wooden block, attached velcro tabs, and "locked" the router into position 8 months ago and have not had a poor connection report from that site since.
Which leads to a discussion of antennas. You should bump the base 2.2 dbi antenna to the 5.5 antenna in poor situations. This does help. Anything fancier suggests to me the need to add a second AP.
As a next step I make certain my firmware: both router and AP are up to date. If you want to ping hack the WRT54G, (I do, but that is just me) follow every discussion on a Forum that people actively share information on firmware releases. You want to be one-version behind this crazy hackers. The BroadBand Reports Linksys Forum is a must site, as is reading their Linksys FAQ:
Do a site search on "wrt54g"
The Michael Erskine trick I mention above does work. I recommend it as the next step.
Finally there are setting where you cannot move the DSL or cable interface to the modem very far, and running long lengths of CAT-5 to make a connection to the router are ugly or impossible.
Use powerline adapters. Leave the cable modem/DSL modem where you must, and use powerline bridge adapters. The notion of powerline causes shudders in the hearts of old-time networking guys. Throw out your old prejudices. The newer powerline standards just flat out work great. You can with no fiddling make a powerline adapter connction between the modem and your router/AP so as to put that router/AP in the best possible location. I have used tons of these from Netgear and Siemans and swear by them. See a very experienced network hands view of the newer powerline adapters in such uses:
A week ago I used to powerline adapters to resolve an WRT54G issue exactly like you describe: cable broadband access, the only place the cable could come in was in the attic. WRT54G, poor reception in spots, generally weak signal. I powerlined to the WRT54G which I moved to the top of a china cabinet on the first floor. You cannot see the thing, but signal strength now excellent at every point where a user could likely roam.
Cost: 89.99 for 2 powerline adapters.
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