Types of governments

To remember this you require to learn some greek roots. The root for government is crat / crac. See here for more on this. Another is arch which is also used.
Now for eg. what is xenocracy ?
xeno means foreign, cracy means rule, so xenocracy means rule by foreigners. Similarly others go. Here is the complete list:

Word	Definition
acracy	government by none; anarchy
adhocracy	government in an unstructured fashion; an unstructured organization
albocracy	government by white people(alb means white, remember disease albino)
anarchy	government by none
androcracy	government by men
anemocracy	government by the wind or by whim(whim means sudden idea, which cannot be explained.
angelocracy	government by angels
antarchy	opposition to government; anarchy
argentocracy	government by money(argent stands for silver)
aristarchy	government by the best
aristocracy	government by the nobility
arithmocracy	government by simple majority
autarchy	government by an absolute ruler
autocracy	government by one individual
barbarocracy	government by barbarians
beerocracy	government by brewers or brewing interests
bestiocracy	rule by beasts
biarchy	government by two people; diarchy
binarchy	government by two people; diarchy
bureaucracy	government by civil servants
cannonarchy	government by superior firepower or by cannons
capelocracy	government by shopkeepers
chiliarchy	government by one thousand people
chirocracy	government by physical force
chromatocracy	government by rulers of a particular skin colour
chrysoaristocracy	government by the wealthy; plutocracy
chrysocracy	government by the wealthy; plutocracy
corpocracy	government by corporate bureaucrats
cosmarchy	rulership over the entire world, esp. by the devil
cottonocracy	government by those involved in the cotton trade
cryptarchy	secret rulership
decadarchy	government by ten individuals; decarchy
decarchy	government by ten individuals
demarchy	government by the people; popular government
democracy	government by the people
demonarchy	government by a demon
demonocracy	government by demons or evil forces
despotocracy	government by despots or tyrants
diabolocracy	government by the Devil
diarchy	government by two people
dinarchy	government by two people; diarchy
dodecarchy	government by twelve people
doulocracy	government by slaves
duarchy	government by two people; diarchy
dulocracy	government by slaves; doulocracy
dyarchy	government by two people; diarchy
ecclesiarchy	government by clerics or ecclesiastical authorities
endarchy	centralised government
ergatocracy	government by the workers or the working class
ethnarchy	government over an ethnic group
ethnocracy	government by an ethnic group or race
exarchy	government by bishops
foolocracy	government by fools
gerontocracy	government by the aged
gunarchy	government by women; gynarchy
gymnasiarchy	government over a school or academy
gynaecocracy	government by women; gynarchy
gynarchy	government by women
gynocracy	government by women; gynarchy
hagiarchy	government by saints or holy persons
hagiocracy	government by holy men
hamarchy	government by a cooperative body of parts
hecatarchy	government by one hundred people; hecatontarchy
hecatontarchy	government by one hundred people
hendecarchy	government by eleven people
heptarchy	government by seven people
heroarchy	government by heroes
hetaerocracy	government by paramours
heterarchy	government by a foreign ruler
hierarchy	government by a ranked body; government by priests
hierocracy	government by priests or religious ministers
hipparchy	rule or control of horses
hoplarchy	government by the military
hyperanarchy	condition of extreme anarchy
hyperarchy	excessive government
iatrarchy	government by physicians
idiocracy	personal rule; self-rule
infantocracy	government by an infant
isocracy	equal political power
jesuitocracy	government by Jesuits
juntocracy	government by a junta
kakistocracy	government by the worst
kleptocracy	government by thieves
kritarchy	government by judges
landocracy	government by the propertied class; timocracy
logocracy	government of words
matriarchy	government by women or mothers
meritocracy	government by the meritorious
merocracy	government by a part of the citizenry
mesocracy	government by the middle classes
metrocracy	government by mothers or women; matriarchy
millionocracy	government by millionaires
millocracy	government by mill owners
mobocracy	government by mobs or crowds
monarchy	government by one individual
moneyocracy	government by the monied classes
monocracy	government by one individual
myriarchy	government by ten thousand individuals
narcokleptocracy	government by those who profit from trade in illegal drugs
navarchy	rulership over the seas
neocracy	government by new or inexperienced rulers
nomocracy	government based on legal system; rule of law
ochlocracy	government by mobs
octarchy	government by eight people
oligarchy	government by the few
paedarchy	government by children
paedocracy	government by children; paedarchy
panarchy	universal rule or dominion
pantarchy	government by all the people; world government
pantisocracy	government by all equally
paparchy	government by the pope
papyrocracy	government by newspapers or literature
parsonarchy	government by parsons
partocracy	government by a single unopposed political party
patriarchy	government by men or fathers
pedantocracy	government by pedants or strict rule-bound scholars
pentarchy	government by five individuals
phallocracy	government by men
philosophocracy	government by philosophers
phylarchy	government by a specific class or tribe
physiocracy	government according to natural laws or principles
pigmentocracy	government by those of one skin colour
plantocracy	government by plantation owners
plousiocracy	government by the wealthy; plutocracy
plutarchy	government by the wealthy; plutocracy
plutocracy	government by the wealthy
polarchy	government by many people; polyarchy
policeocracy	government by police
pollarchy	government by the multitude or a mob; ochlocracy
polyarchy	government by many people
polycracy	government by many rulers; polyarchy
popocracy	government by populists
pornocracy	government by harlots
prophetocracy	government by a prophet
psephocracy	government resulting from election by ballot
ptochocracy	government by beggars or paupers; wholesale pauperization
punditocracy	government by political pundits
quangocracy	rule of quasi-autonomous non-governmental organizations
rotocracy	government by those who control rotten boroughs
septarchy	government by seven rulers; heptarchy
shopocracy	government by shopkeepers
slavocracy	government by slave-owners
snobocracy	government by snobs
sociocracy	government by society as a whole
squarsonocracy	government by landholding clergymen
squatterarchy	government by squatters; squattocracy
squattocracy	government by squatters
squirearchy	government by squires
squirocracy	government by squires; squirearchy
statocracy	government by the state alone, without ecclesiastical influence
stratarchy	rulership over an army
stratocracy	military rule or despotism
strumpetocracy	government by strumpets
synarchy	joint sovereignty
technocracy	government by technical experts
tetradarchy	government by four people; tetrarchy
tetrarchy	government by four people
thalassiarchy	sovereignty of the seas; thalassocracy
thalassocracy	sovereignty of the seas
thearchy	rule by a god or gods; body of divine rulers
theatrocracy	goverment by gathered assemblies of citizens
theocracy	government by priests or by religious law
timarchy	government by the propertied class; timocracy
timocracy	government by the propertied class
triarchy	government by three people
tritarchy	government by three people; triarchy
tritheocracy	government by three gods
whiggarchy	government by Whigs
xenocracy	government by a body of foreigners

So learning the first root will help, if you know the suffix root.