Can heat kill male sperm? are female sperm less susceptible to heat? what are some things to do to promote having a baby girl?

No sure way.: There is no way to "promote" a specific gender. Despite all sorts of gimmicks out there, there is nothing you can do to increase the likelihood of having a boy or girl baby. Save your money. Also, prejudice against a certain gender is not good at all!. You need to work on this before having a child, so that the child (and you) don't suffer if the gender is not what you wished.

Yes: Heat does kill sperm and hot tubs,tight shorts, and such can decrease fertility. There is no difference in this between XY carrying (male) sperm and XX carrying (female) sperm however. The XY sperm tend to swim faster and the XX sperm live longer so intercourse a day or two before ovulation seems to increase the chances of a daughter.Hope this helps.