2, swallow with liquid, usually bedtime.
However I have a fairly slow metabolism and find that I need to take them earlier in the day if they are to work the following day.
They are fairly gentle, and won't do you any harm if you take lots (not that I'm recommending). If they don't work the first day, don't be afraid to take 2 more the following day.
I find them gently effective, and would give them a try over 48 hrs before trying anything more drastic.
Obviously, try to eat fruit and drink fruit juice in the interim. I tend to take the tablets again after 2 or 3 days to try and get things into a more regular pattern.
I tend to suffer every 2 to 3 months, usually triggered by a period of stress, although I think overdosing on coffee blocks me up !!!
HTH