I'm currently using civiCRM 4.4.2 with Drupal 6.
I would like to know if I should upgrade it first to another version, or upgrade it directly to 4.7.5.
What do you recommend?
You don't mention any extensions on your site so if that is not an issue then I think you are as well going to 4.7.x
If you do have extensions then you might want to check things out before going past 4.6.x which is a LTS (long term support) version and has probably had more extensions verified for it than for 4.7.x
Of course if you do have extensions, it helps the community to know if you find any issues on 4.7.x and reporting them back to the maintainers or contributing patches or funds to help ensure they do work on that release.
It depends on your release strategy? There are several options:
If you want to stay on the latest, you can upgrade directly from 4.4.2 to 4.7.5. As petednz mentions, it also depends on if you have any extensions/customizations