i setup a practice mission with the mission builder, i did that over and over again.
target was an airfield with a couple of SAM sites, 3 or 4 tanks for MAV practice, and a smattering of BMP's and other light vehicles for gun and cluster bomb practice
mission had.
ramp start, 3 or 4 WP's.
JTAC.
tanker.
landing.
like everyone has said, read the manual and just practice, finding targets can be tough, i've started reading the mission briefs and make a mental note of asset locations, once the mission starts and i'm sat waiting for the EGI to align i make some mark points where i think they are, that helps a lot.
theres also plenty of guides on the main forums and loads of vids.
just keep plugging away, i've been at it since beta and i'm still terrible so you're in good company