We've mentioned the Single-Biome Planet before. It's an easy (read "lazy") way to create a whole planet:

"What's this planet that I never expected you to visit like? Uh... It's a desert planet. It's covered in desert. It's hot and dry and sandy. All over."

The problem is less one of lack of realism and more that you start training your players to be overly genre savvy and expect all the planets to be like this.

Which of course makes this a trick ripe for subversion. Train your players to think all planets are single-biome planets, and then just when they're comfortable throw them a major curveball. A planet which has multiple terrain types, in a majorly plot-relevant way that is actively dangerous if they assume otherwise. (Details left as an exercise for the reader. We're sure you're smart enough to think of something.)

Transcript

Luke: Hmmm. Well, let's have a look around.
R2-D2: Don't go too far from the ship. You won't be able to understand what I'm beeping.
[SFX]: < squee boop-ting bebioo bing squee boop deep bedoop >
Luke: Don't worry, the ship's not going anywhere.
R2-D2: But you are. Be careful.
[SFX]: < squee ting bebop >
Luke: There's no tech here. What's to be worried about?
GM: The X-wing rocks unsteadily in the swampy water. Dex rolls.
Luke: 14.
R2-D2: 15.
GM: R2, you tip over and fall into the water.
[SFX]: splash!
Luke: Ha ha! I mean... Are you okay?
R2-D2: {submerged} I bet the nearest oil bath is half the Galaxy away.
[SFX]: < doot bedoop-beep bebebioo >
GM: You're completely submerged in murk.
R2-D2: Great. I use my periscope.
[SFX]: < bippity doop bzzt zik-fik-jang bop pow >
Luke: How are we going to get you out of there?
R2-D2: No problem. I can operate underwater the entire time we're on this soggy mudball.
[SFX]: < boodoot doop zik-pik-jang ka-tong doosquee fidooby >
GM: Or you could step onto the land right next to the ship.
R2-D2: Land? What kind of a swamp planet is this?
[SFX]: < nidooby boop fika-pading-dooby >