The difficulty of this Sudoku is Expert. I have tried to apply swordfish, X-chain but seems like it is not valid. But I am pretty sure is my problem because I am still new to the advanced techniques. And the values I putted into the cells are surely correct (because I opened auto-check for mistakes) and here is it :
I have stuck for more than 1 hour already.
I can't speak of any general technique, but I can look at Column 6.
In that column the fifth, sixth and eighth entries are all in the set $\{3,6,7\}$. So those digits are knocked out of the remaining blocks of that column. Thereby $7$ is fixed in Row 9 and $3$ is fixed in Row 1.
Have fun!