Easiest way is to start by reading this article...
http://www.cableforum.co.uk/forum/ar...=12#comment140 and follow the recommendations outlined.
---------- Post added at 23:44 ---------- Previous post was at 23:42 ----------
Also, it's not necessarily a problem to stumble upon your neighbours' WLANs, it's only if you see that theirs aren't secured that you'll want to consider contacting them. However, you should try and configure your WLAN to not share the same channel as your neighbours, so that you don't risk getting interference and degraded performance from both using the same channel.