Once you get that sensation of foreign matter in your eye, relax.
Step2
Gently grasp the upper eyelid (of the affected eye of course!) and pull it firmly down and over your lower eyelid. I've found it helpful to lean over at times.
Step3
Now let go of the lid. I'll bet you feel immediate relief. If not, try again. It's usually pretty effective.
Tips & Warnings
If you have to try a few times, that's OK. Your eye will likely begin to moisten up, which will also help your situation.
Don't monkey with your eye too long. If there's something really tough in there, get medical assistance.
Don't rely on this to get liquids out; flush eyes immediately if needed!