Look, you can't deny that you've asked for sex advice from anyone that was willing to give you their words of wisdom. When you first started thinking about sex, you had to have asked friends, older siblings, or anyone else within earshot. I'm sure you've got some legitimately good advice about being between the sheets but there's some f*cking stupid advice out there.
You probably shouldn't trust your older brother or sister if they start snickering after they give you advice on how sex. They're probably setting you up for failure and you should already be wary of that after all the practical jokes they've played on you over the years.
Google and the internet may probably be your best bet at this point. If you have any doubt with some recently acquired sex advice, you should probably search the internet for answer. Chances are, there's someone out there that's probably tried and failed at whatever sex advice you've been given. Search grapefruit oral and you'll know never to do that again, trust me.