Borg are actually very different from the other race's ships, and you will need to master a different set of tactics to fly them effectively.
That said, pestalence has good advice about taking out the correct targets.
Some other Borgy things to know:
1. Your tractor beam is a weapon. When you're in the tractor panel, charge your tractor and click the "weapon" button. When your tractor engages on it's target, it will be green instead of blue, indicating that it is in weapon mode. It will drain shields first and then start crushing the enemy's hull.
2. Max out your armor at the expense of other systems.
3. Max out your engines after you max out your armor.
4. Create ships with less weapons that fire faster. More hits over time, even though they do less damage will ultimately serve you better.
5. Close on target, tractor, rotate target, fire until dead, repeat.
Now stop playing single player and come join us on a Dynaverse server!