As a writer of skirmish games I often say that you cannot have enough terrain, and that no piece of terrain should be more than a fast move from any other.

However, as noyjatat says, we need to know what size game you are aiming to create; skirmish, large skirmsh/small unit action, company level, regimental level etc.? Are we talking formed up units or individual figures?

Here is an extract from one of my games to give you some ideas:

The following options are suggested for setting up terrain:

1.       Cooperation.  The players cooperate in producing a pleasing and suitable terrain setup, perhaps referring to actual landscapes.

2.       Place Then Choose.  One player lays out the playing area and identifies where troops can deploy onto it.  The other player(s) then choose their deployment location(s); if there are more than 2 players, roll for the order of choice but the player who laid out the terrain will always go last.

3.       Defender’s Choice. If the scenario involves an attack against a defended position, then the defender may choose the terrain.

4.       Alternating Choice.  Each player is allowed to pick an agreed number of terrain pieces which are then placed one at a time; roll to determine the order in which the players place each piece.

I generally prefer option 1, and often play using option 2. Note that all these ideas require no cards or other complicating factors.

You do need to determine what each type of terrain does in the game. Does it block line of sight? Does it provide troops and/or vehicles with cover and if so, how much?