Not being able to conceive after 12 months of regular unprotected intercourse.if u are more than 35yrs this time limit is reduced to 6months.
Semen analysis preferably after 3 days of abstinence. Baseline scan during period to know uterus and ovaries and to count no of antral follicles. D2/3..fsh to know ovarian reserve. Tsh and prolactin if cycle is irregular or suspecting ovulatory disorder. Hsg(d8-10)..to know tubal patency.
Yes smoking reduces spermatogenesis,sperm motility and quality also.
In a regular 28-30days cycle. 12th to 22nd day is considered as fertile period.