Every game of Legion starts with you and your opponent determining a scenario to play from a selection of Battle Cards. This is done by first dealing 3 cards from each category and then taking turns eliminating options until both players have eliminated 2 cards each. This means that you cannot guarantee that any one card will be used (as some cards are not even dealt as an option), but you can at least get rid of some of the least desirable options.
For some quick tips when it comes to eliminating Battle Cards, check out this article I wrote for Imperial Terrain: The Battle Begins: Battle Card Selection.
Below are links for articles on each Battle Card. I discuss when you may want to push for or avoid playing each card, and then offer some strategies you might employ to play them to your advantage.
Intercept the Transmissions
Recover the Supplies
Sabotage the Moisture Vaporators (Priority Supplies Battlefield Expansion)
Advanced Positions (Priority Supplies Battlefield Expansion)
Minefield (Priority Supplies Battlefield Expansion)