How do you plant the idea in a woman's mind that she should build muscle?  Maybe not become a bodybuilder, but at least start building more.

eg. I was thinking today about if I knew a fit, gym going - but not muscular - woman in my street, could I drop something in her mail box that might plant an idea in her head?
Or if I knew her email address, could I sign her up to something - a website, a newsletter?
Of course if you actually are on speaking terms with a candidate, there are more options.

ie. what tools do we have to spread the gospel of muscle?

What strategies have you tried?  Does it differ by how well you know them?

Tell them to lift with you

Bingo. Any woman with the will to become muscular will likely have the will to resist inert persuasion.

Get them to lift with me, I like that idea, yes

What about for those I don't know real well?  T-shirts I could wear to inspire them?  Insta**** accounts I could mention to them?  Magazines I could recommend in passing?  Crossfit giftcards? 
 
Ideas?  Which thing ISNT creepy haha

Tell them about the benefits of lifting weights. It prevents osteoporosis and reduces weight. I find that women are more health conscious these days and take better care of themselves. Weight training is a great method for weight loss ( or muscles mass gain in replace of fat ). 

First of all , inspire them with your own role model - bit active &fit ,urge them to work out with you
talk a lot about benefits of lifting hard & calm down their fears of "getting too muscular" ,show them picures of fit woman
but not  "hardcore" at the beginning
then enhance the level of training with them,show them more & more muscular role models ,but only step by step
so that they can get accustomed to it  .................

and hope they will follow your path

wish all good luck !?.................

First of all , inspire them with your own role model - bit active &fit ,urge them to work out with you
talk a lot about benefits of lifting hard & calm down their fears of "getting too muscular" ,show them picures of fit woman
but not  "hardcore" at the beginning
then enhance the level of training with them,show them more & more muscular role models ,but only step by step
so that they can get accustomed to it  .................

and hope they will follow your path

wish all good luck !?.................

Yep - small steps is what I'd recommend - shoving a photo of Helle Nielsen in their face and saying that's what I want you to look like will only end in tears (ours)!

Get them to lift with me, I like that idea, yes

What about for those I don't know real well?  T-shirts I could wear to inspire them?  Inst@gram accounts I could mention to them?  Magazines I could recommend in passing?  Crossfit giftcards? 
 
Ideas?  Which thing ISNT creepy haha

Dude all of these are creepy. I mean do you expect a woman to start bodybuilding because some stranger asked them to so he can get his rocks off to her? And you thinking you can make a stranger change their whole lifestyle to fit your ideals is borderline sociopathic. I'm all for more women taking up bodybuilding but it ultimately has to be something they want for themselves. A much more realistic goal would be to invite a girl that you already know to the gym with you. If she takes to it and enjoys it then maybe you can convince her to gradually lift heavier. But if she doesn't enjoy it and you try to force her to you're just going to come off as creepy and probably turn her off weight-lifting all together.