You can use Horoscope by date of birth to find the star of the boy and girl
Nakshatra Matching plays a small part, say 10%, in Marriage Matching. Ashtakoot Guna Milan
is one of maybe 5-7 steps in the overall matching (kundli milan) process to assess compatibility.
Star Matching for a happy marriage,
a study of 30+ couples' marriage life throws more light on this
See Nakshatra Porutham,
for Tamil / South Indian porutham calculation