Cleaning up audio with Audacity, need help

[Chainmax]

I'm currently trying to enhance a bad audio source I have. It has a nasty humming sound in the background and some clicks/pops/whatever it's called. Sometimes, there is also some weird echo with voices. I previously used the WinAmp DFX plugin but need something more advanced. Can anyone point me out to an easy guide on how to clean up and improve bad audio sources with Audacity?

[Valky]

if you are using Linux, then I have found that software called 'GWC' is superior to anything else I have tried (CoolEdit, Audacity) when cleaning "humming" and other kind of noises. It's also freeware and very easy to use. Some guides can be found on their homepage.

Doesn't exist for Windows :(

[joeyc]

Audacity has a noise reduction feature in its effects menu. Select a portion of the audio where there is no dialog or music (just the noise; possibly the first few moments of the file) with the mouses left click held down. Open up the noise reduction feature of the effects tab and click on Get Noise Profile (step 1). Then in the noise reduction window click on Remove Noise (step 2). This should remove the noise from the small portion you are currently workin on. Play this selected moment and if you are happy, click on Undo Noise Removal in the Edit tab and select the entire length. Click on Remove Noise again and sit back. The sliding scale in step 2 allows for the level of noise removal: at the top, voice and music are distorted; at the bottom, little reduction take place. You can experiment by Undoing noise removal and sliding the slider to another position and removig noise again.