Summer,
Dun need so kiasu lah..

Eat 3 mths before TTC can already. But if you are not using any contraceptive, then better take now.
5mg (1 tab) a day is good enough. Normally I just take in the morning with my other pills. But if wake up late, then eat later. No need to eat after food.
I dun think there's any side effect as it's just a form of Vit B.
http://www.medicinenet.com/folic_acid-oral/article.htm
SIDE EFFECTS: Folic acid usually has very few side effects. If you have any unusual effects from taking this medicine, contact your doctor or pharmacist promptly. A serious allergic reaction to this drug is unlikely, but seek immediate medical attention if it occurs. Symptoms of a serious allergic reaction include: rash, itching, swelling, dizziness, trouble breathing. If you notice other effects not listed above, contact your doctor or pharmacist.
If you are staying near the east side, I will strongly suggest Dr Heng Tung Lan at Bedok (delivers only at Eastshore) I really liked her a lot and was glad that she is the one delivering me. She's full of confidence and will let you feel you are in good hand from the start till the end. Eastshore hospital is very nice too! Very homely place. Nice food, nice nurse!
Three's a thread on her too in the forum. Just do a search.