I have just taken up playing the "classic" UNREAL again (playing it since 98) in Unreal mode. It seems the skills I've honed playing UT, strafing, jumping while firing etc...has made me an UNREAL wrecking machine.
Skaarg, Sliths, Pupae, Titans......no match.
* Keep moving
* Make use of the powerups and ammo.
* Retreat, recover and go back at em whenever possible.