You need a prybar like a long one a few feet long with a big Handle, Sears sells them for $20-30.
You jack up the corner or end of the truck then you insert the pry handle between the geared hub and the control arm and give it a yank to see if theres any give on the ball joint, you do the same on the upper. If there's no play, you are good, if there's a little play you should swap it out.
The manual states something like 1/16" of movement is acceptable, but I usually find the two extremes is more common, either no movement or a 1/4" of play. You can also grab the wheel while jacked up in the air at the 3 and 9 o'clock position and give it a good shake, this will also test the joints in the tie and radius arms.
I should throw a video up on the tubes to show how to do this, i got a good one from Tustin showing a really bad ball joint gone on an Alpha.