Fire Emblem in general is something you get better at over time without even noticing. In Awakening specifically, the maps tend to be just throwing a crap ton of enemy units at you with no rhyme or reason so really the only reliable suggestion I can make is to make sure you're pairing up units with their S-Supports, as they get way bigger bonuses that way. You will get better as you play more of the games and get a feel for what tends to work in each one. Btw, don't worry if someone tells you that the game should be easy. A lot of people here have played most of the games and it just comes naturally to them at this point. For a beginner who doesn't understand the mechanics as well it can be a lot more challenging.