Honestly? Very timidly, after a lot of reference searching. I'm a little less confident on backgrounds than I am with foreground stuff so I have to prepare lots of material to draw from.
The main thing I keep in mind is the colour - I like to saturate the backgrounds a little bit less than the foregrounds to help them pop. I sometimes put a bit of gaussian blur on there if the bg is far back. I kind of just play around with these until it looks okay. I also really like to use gradients in the background, since my comic has a bit of an 80s theme to it.
I always hated to draw backgrounds, so I didn't pay so much attention on it. I only used some brush in Photoshop to diversify it. After a while I realised that it can't go on, so for a while I try to add more backgrounds. I make at least one ot two panel with background and the rest can be less detailed. For Furusato House I already started to draw backgrounds by my imagination, but in Dreamcatchers sometimes I can use references, like for this page:
I used to worry a lot about perspective and that everything is concrete and fleshed out. With the comic I'm currently making this would take so much time I eventually landed on an approach where I almost tease at how stuff work and almost draw stuff orthographically but I split each environment into layers that has different depths. Rather than having a completely "dynamic" perspective in the image. I like to focus more on the colors, mood and composition.
I kinda hated backgrounds because I didn't understand how perspective works. Now I'm the complete opposite after some studies and training. So far I very rarely reuse old backgrounds. It's too much fun for me and the scenes are very different anyways. I don't use a background on every page thoug, because it can make the charas less relevant.
I use a plugin in photoshop that adds perspective lines, though most of the time I just freehand.
Often, I pour through reference photos of items I find interesting or relevant to the setting, then try my best to reinvent them. Though, I will admit that I can be lazy with that every so often, and not do enough research for my backgrounds..
My main influences are Peanuts and Tintin - so that's led to a style which uses minimal backgrounds and a tendency to draw the straight-on without perspective. However, I do make the colour pallette do a lot of the heavy lifting - having cats who are mainly white in colour as the main characters means I use colour fields in the background to provide enough contrast to make them pop out of the page. Clarity is all.
However, occasionally I decide go mad and do some serious background work using photographic reference...
My approach is heavily fed from illustration techniques and your good ol' trial and error. Emphasis is almost always on characters/figures so the work of building an environmental setting often gets pushed to the backburner. "Guuuuh, I don't wanna draw door knobs and light poles and little pieces of trash on the pavement, I wanna draw a pretty face or an ugly monster!"
Those elements of a scene totally do play into perspective, though. If they're tailored into the mood/how emotion plays out per panel, background aspects become cool little investment properties. Which is why scenes with little flowers with heart-shaped centers growing in a flowerbed impact a character reading a love letter they found in their mailbox~ CUTE.
Take the details and make them work for the scene in lieu of making them work for basic ideas. In the rough sketch phase, I designate quick, fast lines in negative spaces and flesh them out as I go as a complement to that negative space. As the brain processes just how the characters are presented at an angle with respect to setting, perspective works out organically.
So, it's more a game of "this is how it'd be seen" instead of "this is how it is".
For the comic I edit pictures of public places that I take myself. This is after a lot of trial an error with so many different styles of creating backgrounds and this actually looked the best since the blurred and painted over background make the characters stand out a lot more and work with my art better than the other styles of bg's. It's also faster since I make a fully coloured 20-30 panel weekly comic so this type of background made the most sense.
I made a tumblr post explaining this is more details.8
I'm not the best at backgrounds since I feel like I don't plan them out well enough. When the backgrounds are not supposed to be focused I like to do them without lines to give it a watercolor feel. If they are supposed to be in focus I will line them but I'll still generally paint them in the same way except with lines.