I personally would like a tag for when a girl is holding a penis and putting it in her. Like, right before it goes in, and it's touching the vagina.

Seen in the bottom right corner of this: http://danbooru.me/post/show/339276/blush-censored-dragon_quest-dragon_quest_viii-fell

I've run into a lot more posts, so it'd be great to have a tag.

If tagable, guided penetration would be a better tag, to complement the existing guided breast grab.

You're right.

guided penetration is a very good name for such a tag. Simple, yet perfectly descriptive. +1

Yeah, go for it.

Randomly found another one. http://danbooru.me/post/show/217856/anal_hair-anus-ass-censored-condom-cowgirl_positio

Also, I don't know all the rules here, is there something I should do to take this further towards being a reality? Is there a form to fill out or something?

Just add the tag to posts that deserve it. That's all there is to it.

Also, when linking to a post, use "post #XXXXXX" (without quotes, and substituting the post number for the Xs).

Example, using the post linked above: post #217856