First situational awareness.

Be aware of what is going on around you. That way you may or should spot what is going on around you. Then maybe you can avoid the problem all together. Then if it does happen you know some of the available options.

Fight or Flight.

Bail if you can.

Fight if that is all that is left.

Get your back to something. That way if they can only come at you from one direction.

Use anything that is in the surroundings as a source of weapons.

Fight all out. do as much damage as you can. Try to make is painfull and bloody as possable. Do your best to make the damage as obvious as you can. Of course as mentioned target the leader and/or the biggest ones first. You might discourage the rest.

Do the worst you can. That way even if you lose you can take an honor guard with you.