Not any real advice apart from studying what the masters have done before you, but I will say this: it seems that when it comes to comics, mastering backgrounds is as much mastering what not to draw as it is what to draw.
I'm in awe of artists who are able to portray vast, detailed landscapes and settings without actually wasting time in drawing all that much detail. It's something I'm constantly working and probably failing on. It must be something that comes with years of experience and practise, but when it works, I actually prefer it to a background that's just detail detail detail, which can be overwhelming to the eye.