I have to say... Awakening is really over the top with the 'Let's pile as many units onto one target as possible! :D' layouts. Was FE always this way? O_O
As a note for Brill, who I know wants to get this game eventually: Place your Avatar's Asset in Magic (and please don't place the Flaw in Defense! D:) for a very entertaining early game. Apparently people would recommend otherwise, but for a casual player, this gives you a potent magic-user
with reasonable defenses. Your other choices for magic-users tend to curl into the fetal position and start sobbing when enemies start waving pointy objects in their faces, whereas the Avatar can take a few hits and stay upright.
Also, you want to concentrate on high-DEF units, due to the aforementioned dogpile and pointy-objects issues. Chrom starts to lag on the DEF front after a while, but he tends to kill enemies too quickly for them to ask "Hey, what's your Defense?" Incidentally, that's how one often has to deal with magic users, as there are in fact
anti-flyer tomes in this game. Say farewell to being able to lean on your Res alone!
Speed is also a very important stat in this game. Without Speed, you tend to get doubled by New!Bandits, which are called Barbarians and carry unusually interesting Speed stats for axe-wielders. So be careful with Knight-like units!
(Hint: Your Cavaliers are good in this game. VERY good. ...That's not a spoiler, right? :D;;)