Prepositions indicate relationships between words and ideas. Most prepositions deal with location and are easy to learn.

above	below	over	under
inside	outside	around	through
beside	beyond	behind	in front of
near	nearby	by	next to
up	down	toward	along (side)
before*	after*	during	since*
with	without	within	until*
into	out (of)	off	upon
between	among	except	but*
like	as	than	about
despite	in spite of	beneath	underneath

* These can also be used as conjunctions.

Some prepositions, however, have more than one meaning and can be very confusing.

in	on	at
to	from	for	of

Generally, in, on and at indicate location.

See also : Grammar - Prepositions of Location

To and from imply movement toward or away from something. However, to can also function as part of an infinitive.

See also : Grammar - Infinitives, To V or Not To V

To and for can introduce indirect objects.

See also : Grammar - Indirect Objects

For and since can also indicate duration.

See also : Grammar - Present Perfect Progessive

Of is used in partitives (all of, some of . . .) and other expressions.

See also : Grammar - Quantifiers

Many prepositions are also used in expressions.

See also : Grammar - Preposition Collocations with "Be"; Verb and Preposition Collocations

For further reference:

Grammar : Prepositions and Time Words

Grammar : Adverbs and Prepositions

Grammar : Prepositions and Subordinators

The Preposition (from Grammar Bytes)