*edited - found this on net and it sounded better than my original post
*
Open your mouth, press your tongue down and look in the mirror to see if you can see it, or ask a friend.
It's probably better not to swallow it (depending on the size) as your doctor could get it out fast if it's still high up or go to the accidents and emergency ward of your local hospital so they can get it out straight away without it causing damage on the way down.
If you think you've swallowed it, eat lots of bread or oats and drink water to make the passage easier so it doesn't scrape on the way down and so it doesn't go into the windpipe.
If it scrapes on the way past you might need an anti ulcer treatment or an anti-inflammatory. This is likely if you have pain 4-5 days after the fishbone.
Do NOT panic, it doesn't help anything and seek medical advice if you have pain and especially if you have trouble breathing (which can also be due to panic so try not to worry)
If the hospital can't see it and you still feel something (note: this could just be an ulcer or a scar) they might do a fibroscope test (tube through nose going half way down the throat) to reassure you. If the pain is lower down say so, as this is the domain of the gastro-enterologist who would also put tubing down that goes lower, but this is in the worst cases.
Above all, do not eat your fish in the same mouthful as other foods and chew it slowly. Or avoid fish with bones, try scallops