my 2 p worth.
You must have something to eat before you go.
If you are "squeamish" don't look when the needle goes in (i never did)
If you do feel a bit "unwell" do say so, don't be shy, most first timers are a bit unwell (no i dont mean sick, just a bit...light headed)
Do have the tea and biscuits afterwards (really they do give tea)
The odd thing is for (me) the bit that hurt most was when they jab your thumb for a sample, they really hurrts more than the nedle going in, (i never felt the needle going in)