When do i take clomid?

You usually start taking clomid during your period and the consumption starts on the third, fourth or fifth day, depending on the advice of your doctor. Clomid is consumed for five days. So if your doctor gives you five pills then its one pill a day, if he gives you ten then its two pills a day and so on and so forth. Initially he will start you off with five and then if it doesn't work he will raise the dosage or double it to ten.
Ideally however you should start on day 9 of your cycle which means that you will ovulate around the fourteenth day. During this period choose to have intercourse every other day so that it gives your system and your partner's adequate time to recuperate and the semen count will also be replenished thus increasing your chances of conceiving. So from the 14th day of your cycle till the 19th day of your cycle you should be able to conceive.
Coming back to when you should start Clomid dosage. Your doctor will more often than not tell you that it is better to start on day 5 (cd5) of your cycle rather than day 3 (cd3). Yes both of them do remain usable options and both have their setbacks so the doctor, after examining you thoroughly will be able to tell you which works best for your body and cycle.