Human tip: When going against an alien that isn't a dretch or basilisk, predict when the alien will chomp/swipe. Crouching before then will keep you from being dealt a head shot; the alien will either hit your body or miss you completely (too high up). Then, you can get back to confusing the alien.
Just don't do this when you have a helmet, especially not against rants 0_o
Anyway, I should probably contribute, so here goes.
Always use wall-walk as a dretch, never use the ground.
it takes some getting used to, but you will grow more comfortable on the walls and use your sense more, because uneven walls will kill you LOS.
Oh and setting your WW speed to fast/instant may give a you a headache at first, but will help in the long run.