WalkingArt,
I conceived last time on my first round of clomid. Common symptoms are hot flushes/feeling hot, night sweats, moodiness, dizziness, blurred vision. These are usually mild. I was on 50mgs when I conceived last time and this month I am on 100mgs - I had virtually no symptoms this month at all - a little dizzy at times... Drugs affect different women differently so bear that in mind... OHS - ovarian hyperstimulation syndrome is a rare side affect. There of course is a higher risk of a multiple birth - usually twins, however the risk is only increased by about 10 percent.
As Emmydee said the higher estrogenic affect of clomid can thin the endometrium in some women. A lining above 10mm is needed to feel confident that a pregnancy can successfully implant/be maintained. This is why many obs will do an u/s after your first or second cycle just to check that that isn't happening for you. The older you are the more likely that this will be a side affect. (I am 39 and my lining is great this month). For this reason too many obs will do 3 months have a rest month and go for another 3 months. As someone else said the majority of pregnancy's on clomid will occur within 3 months and usually it is used for 6 months and then reasessed.

I hope it works for you quickly and effectively and that the new year sees you holding your baby safely in your arms.