This detailed video by Arjun also shows how to tune a sitar. 

Guide to Tuning

Sitars are usually tuned to C# or D. Below is a chart to convert Indian Sargam to Western notation.

C# Tuning
Sa (1st note) = C#
Komal Re (flat 2nd) = D
Shuddha Re (natural 2nd) = D#
Komal Gha (flat 3rd) = E
Shuddha Gha (natural 3rd) = F
Shuddha Ma = (natural 4th) F#
Tivra Ma (sharp 4th) = G
Pa (5th) = G#
Komal Dha (flat 6th) = A
Shuddha Dha (natural 6th) = A#
Komal Ni (flat 7th) = B
Shuddha Ni (natural 7th) = C

D Tuning
Sa (1st note) = D
Komal Re (flat 2nd) = D#
Shuddha Re (natural 2nd) = E
Komal Gha (flat 3rd) = F
Shuddha Gha (natural 3rd) = F#
Shuddha Ma = (natural 4th) G
Tivra Ma (sharp 4th) = G#
Pa (5th) = A
Komal Dha (flat 6th) = A#
Shuddha Dha (natural 6th) = B
Komal Ni (flat 7th) = C
Shuddha Ni (natural 7th) = C#