Easy casual? You won't need any help at all lol. Make your units go to level 20 and then use a master seal (You'll have to wait a lot to get to level 20). Don't use Frederick much or at all, because he doesn't grow much. Make some pairings, and remember the weapon triangle.
Oh, and try to recruit all the characters that appear. Some need a special requirement but most are just by talking to them with Chrom.
This is actually pretty bad advice for Awakening. Awakening plays differently from other FEs.
When in a pre-promoted class, use a second seal at level 10. Get all of the low level skills you want before using a master seal and then bouncing around the promoted classes.
Frederick is just fine. He's promoted yes, but you can second seal him back down to a pre-promotion class. His growth rates are actually in the same range as everyone else.
Make sure you get Chrom to an S-Rank pairing ASAP. He's the only one on a time limit and if you somehow manage to REALLY REALLY mess it up, he'll marry a generic villager and that will hurt another unit down the line.
Really, Awakening is "Baby's first FE" if you would. Unlimited EXP thanks to second seals means its impossible to have a bad character, the only question is how long it takes until they have max stat everything. Pair Up makes it even easier and harder to lose with absolutely massive stat boosts for S-Rank pairings + free extra attacks/nullifying attacks. You basically don't need any sort of strategy for the vast majority of the maps as well. On Easy Mode it is completely brain dead.