What is the default button to bite someone during combat?

[Akfiz]

I haven't played in a long time and the key bindings aren't very useful.

[lord-of-misrule]

Stun them, then hit F.

[Akfiz]

How do I stun them?

[Zeris]

If you're using one-handers, then your off-hand weapon (stakes, bludgeons). Some firearms also have a stun stat if you build into it, and most blunt weapons have higher stun ratings than edged ones. The spring ability also has a stun element to it.

Using any of these, just pay attention to the gray bar underneath an enemy's health bar. Once it's empty, they'll be stunned and you can feed on them.