Any tips on how I could do this?
I haven't done it on the Streak. I do remember seeing a discussion on how to do it several months ago. Do a search on xda (I think). Sorry I can't point you in a more specific location.
As for your wifi router, changing the channel frequency is router specific. I'm in the USA and the att tech showed me how when he set up my dsl service. If I remember correctly, there are 15 available channels and he said all routers are set to channel 1 by default when manufactured. I couldn't get 10 feet away from the router without dropping wifi. After changing channels by trial and error, I found one that had a strong signal throughout my entire house and into my yard.
My router at work can be set to 2.4GHz or 5.xGHz which increases the signal. I can also change channels on it from the prefs menu. I do have wifi analyzer on my Streak and it is set for all channels to help find the strongest one.
Hope this helps. It has been 2 years since I modified my router channels and I don't remember more specifically, as this isn't something I do regularly!