Basic tutorial for getting rid of all those spare sprues lying around and getting a more flavoful base than the standard rocks and grass.

What you'll need:
Plastic Glue
Green Stuff
Spare plastic sprues
Some sand

 I'm using a Cygnar Trencher on a 30mm base.Grab some sprues and set them aside, try and keep them about the same length, and at about shoulder height to the model you are basing.

Now, trenches are muddy, so lay put down some Green Stuff along the base to make  some slushy mud as well as provide and anchor for the sprues which will form the trench walls.

Now, grab those sprue bits you cut earlier and line them up along the side of the base you want the walls to be on. For this model I chose to make it look like he is running out a trench system, so the wall will only be on one side.
I'm going to add a sign made out of plasticard on the side, as bare walls look sort of boring.

Time to add some sand. Add some plastic glue to the base, and now dunk the base in some fine to gravely sand. If you've ever been to the beach, you'll know that sand get everywhere, so be careful you don't get your model covered in the stuff.
Now clean up the base and make sure that no glue/putty/sand has landed on your model (unless you want it to). After a quick slap of paint, here is how he came out:

I added some snow to suggest that the unit he is with is in the north. The paint work isn't to great. A lot of my paints are drying up or clumping up, a restock is soon to be in order. Anyway, hope this has proved useful.