Ever since the American Civil War, when long-ranged, accurate guns became common issue, infantry's mantra has become "stealth is wealth." Or, more literally, "stealth is life." Doubly so when mobile fortresses (armored fighting vehicles) are about.

To summarize a lot of the wisdom already mentioned on this thread, the smartest doctrine when facing vehicles is: 1) Hide; maybe it'll go away. 2) Call up someone who's equipped to deal with the nuisance; i,e., tanks, tank destroyers, artillery, air strikes, et al. 3) If all else fails, fight as dirty as possible. Get close; AFVs are open-country monsters. Use mines if you have them (or IEDs; look at Iraq). Do not rush, yelling (after 2004, that tactic utterly stopped in Iraq, since those who practiced that tactic failed to survive it).