
I suggest starting carefully and giving them time to think things over + consent before bringing out the toys. (It is also easier to ask them to clean their ass well.)
Also, try to look for their toys together (online) and start with something that is small and isn't "scary" looking. Discuss how they want to involve their ass. (do they only want to have a buttplug or your fingers, do they want to be on top, would they like for you to dominate them, etc.).
Gently experiment what does the trick for them (where, how, what): locating the prostate might need some prodding around. Provide a lot of positive feedback during and after the butt-action. (spoil them without being demeaning.) Guys have some masculinity fueled pride after all.
Finally, do not expect them to take something large on the first few times. You have to slowly work up: make them get used to and accept the smaller toy before moving on to something a little bigger.

yess thank you for explaining that!! there are a lot of young inexperienced ppl and you definitely don't want anyone to have a bad first experience.
You also have to keep in mind that this process might go over a few days, weeks... even for girls trying anal. And after you or ur partner has consented and cleaned themselves etc. it's critical that they are prepped and 'stretched out' so that it's not super painful.
I ALWAYS cringe when girls tell me they allowed their boyfriend to try anal and they just shoved it in. Nooooooooooooo!!!!!!! don't get ur education from porn! they do so much behind the camera.

Oh yes I agree that most porn, manga, etc. just ignores or skims over the prep.
It usually also takes a lot of foreplay for guys to open up, so I suggest that people who want to peg their guy are experienced in that or read up on it.
Especially if you are pegging you need to make sure you understand your partner's body and kinks: after all, you want them to like what you are doing, so no surprise whipping, surprising size upgrades etc without consent. This is also practical since the ass tends to constrict when people are surprised or afraid or just tense: if you go overboard, pegging might quickl become uncomfortable for your partner.
An example of how you could make sure your partner consents fully while still keeping the "surprise factor":
1) show the toys to your partner.
2) discuss what he wants to try and in which conditions and let him pick multiple.
3) you make the final selection of a combination of the picked toys and keep the combination a secret.
Make sure you talk about it and they agree (don't pressure them into agreeing) before you do it.
ladies, it's time to peg ur man