These are the most frequent prepositions, grouped by meaning. Each governs a particular case in the singular — remember that in the plural almost all switch to the dative.
Place
uz galda
on the table
zem galda
under the table
virs galda
above the table
aiz mājas
behind the house
pie loga
by the window
starp mājām
between the houses
uz means ‘on’ with the genitive (uz galda) but ‘to / onto’ with the accusative (uz Rīgu).
Direction
uz Rīgu
to Riga
no mājām
from home
pie ārsta
to the doctor
gar upi
along the river
Time
pirms pusdienām
before lunch
pēc darba
after work
pa dienu
during the day
ap pusnakti
around midnight
Other relations
ar nazi
with a knife
bez naudas
without money
par grāmatu
about a book
pret vēju
against the wind
caur mežu
through the forest
In sentences
Grāmata ir uz galda.
The book is on the table.
Es braucu uz Rīgu.
I am going to Riga.
Mēs runājam par tevi.
We are talking about you.