Do u always have to have sex with d man on top to conceive? i heard u should cuz its deeper n its the best way to conceive. is there a "best" way t.c?

No.: There's no best position; conception depends more on timing of ovulation (egg release), and quality/quantity of sperm.

Not necessarily: The object of intercourse is for the deposition of sperm as deep in the vagina as possible. You need only be conscious of your periods of maximum fertility (look up mittleschmerz) and to recline for 1/2 to 1 hour following to allow the best chance of penetration. Do not worry about fertility until about 6 months of trial has gone by.