Typically, the sitar is tuned to the raga that is being performed, as a result there isn't one standard tuning for the sitar the way there is for the guitar. In general folks seem to tune the sitar to c, c# or d if they are playing solo.
I have read that it is best to first tune the sympathetic strings and then to tune the main strings and this typically is what i do for the sitars in the shop. I have also found that a chromatic tuner that produces tones is very very handy as it is far easier to tune to the tone then it is trying to tune to the needle on the tuner. A gentleman by the name of Tim D. Russell put a series of tones out on the internet that is free for download. i have found these very useful as well. They can be found at the link below.