Most simple way and fair that i can think Roll a D20 before initiative: 1 Aquatic 2 Nothing 3 Nothing 4 Nothing 5 Desert 6 Nothing 7 Nothing 8 Nothing 9 Mountain 10 Nothing 11 Nothing 12 Nothing 13 Jungle 14 Nothing 15 Nothing 16 Nothing 17 0-G 18 Nothing 19 Nothing 20 Nothing You will see how fast people start taking multiterrain units (not that great for us really)
start adding them to your own games. Build tables with dedicated and clear terrain zones and add a reccomendation to the table for other players. Eventually the perception will change
A couple of water features/ponds and plastic trees in planters were an easy way for me to get more terrain skills in. Not sure about how to get mountain or desert terrain in, maybe a golf course with bunkers and rockeries :P
For Mountain i would use many many Stones and plenty of level change over the board. But to build a good looking mountain board is another story. Desert is easy.... just sand, dunes, sand sometime Rocks and some sand or some Oasis surrounded by.... more sand
Mountain also covers snowy terrain which can make for a cool looking board. Lots of snowy battlemats available and snow drifts are pretty easy to make. This is where the plastic trees and plants in, er, planters come in, you need jungle to move through them, but they add low-vis or saturation zones. Holo-ads or antennae can apply white noise due to interference.
Our local meta regularly plays with terrain rules. We have specific areas/terrain pieces set up to represent different types of terrain. It makes for more interesting games. I think the most dramatic outcome has been that it makes for a more survivable game. It makes profiles shine where the usually wouldn't compare well to other profiles.
Roadworks, instant Mountain terrain in urban environs. (building sites make good areas for different terrain rules) Aquatic can be as easy as a crashed tanker spill across an area/road. Desert can likewise be spilled powder, grains or sand/cement. Have crashed cars as centre points for zero vis zones, with dangerous terrain rules (18+, dam 10 ARM) for models standing in them. Downed power lines for White Noise, aggressive terrain (17+, dam 11 BTS). Rule all buildings' interiors as saturation zones with low/poor visibility (that's a bit brutal IMO). Have the entire board poor vis with limited range 24" but any model inside a building, or within range of a light source is lit up and fully visible to anyone as normal, ignoring the range limit.
If you want "instant" terrain without the hefty setup, you could just do what I did and buy cloth swatches. They're usually a dollar or two at WalMart or a hobby store like Michael's, come in multiple colors and cut easily. Iron them flat and you have a bunch of thick terrain zones. Black for mountain rocks, green for jungle, blue for water, purple for zero-G... it works out great for our local store. And then you can decorate to your leisure. Here's a picture of a local table at a tournament I ran with mountain terrain on it: https://imgur.com/9eeij92 And one with Zero-G: https://imgur.com/CS0afBS I've played twice on Aquatic Terrain with Varuna so far. My big takeaway: When almost your entire army can pretend the table is a normal table while your opponent is constantly cutting off orders it just enhances how powerful VIRD is in ARO. You can easily slide up the board with a ZC or Croc in any terrain, but Aquatic is choice since it has a lot of Very Difficult terrain in it, and it hacks warbands off at the knees if you push or pull them into terrain by standing in it. Althought I wish Terrain skills let the Echo Bravo AD into a terrain zone-- that's the one time Aquatic on a board edge will get you.
There is really good flat terrain for Warma/Hordes, irregular forms in mouse pad with water, debri or forest printed on them
