Many mobs (monsters) have specials that summon more monsters, usually
of lesser value than themselves. (guards)  Usually the guards add to
the danger of a battle, thus making an already difficult monster even
more malefic.  However, there are some ways that such summons can be
used for personal gain.  These methods are, at best, frowned upon, and
at worst, illegal to mud rules.  Should you find that you are falling
into any of these behavioral patterns, take warning that what you are
doing is not quite fair to the system, and that you should stop or
face possible consequences.

1:  "Follower" guard exploit.  A relatively rare occurance, though
very easily exploitable.  This occurs as thus:  The monster summons a
guard, or group of guards, you retreat, and the guards follow you. 
You easily kill the guards, loot the corpses, and run in again to wait
for another summoning. -  This exploit has been proven as illegal, and
if you find any summons that follow you that could be easily
exploited, it should be reported to a wizard IMMEDIATELY.  Failure to
do so can result in forced reincarnation.

2: "Healer" exploit:  This is largely based on skill, and is thus
ambiguous, as there is still a danger factor.  This is done with
monsters that heal themselves, or have fast regen, or with the help of
a biomancer.  It is done by running in, waiting for summons, killing
them, and then running out, then letting the monster either heal
itself, or sending in a biomancer (or equivalent) to heal him before
going back in.  Though it has not proven too much of a problem, as
this technique still involves danger, it is still recommended that it
is avoided.

3: "Auto Summon" Exploit: Some monsters summon minions whether
attacking or not.  Usually attacking the summonings causes them to
counter attack, thus initiating battle.  Should it not, it should be
reported to a wizard IMMEDIATELY.  Even if aggrivation occurs,
exploitation is still relatively easy, as waiting for a new minion set
can be done at no risk.  This behavioral pattern should be avoided.

There are many more methods of exploitation possible, these examples
have been discovered through observation and information gathered. 
Should you have even the slightest doubt in your mind that what you
are doing unbalances the game, ask around in multiple channels, or,
failing that, ask your local Wizard.  Also:  If a Wizard asks you to
stop something, stop it IMMEDIATELY.  

See also: Bug, Wizard, immortal duties, rules