The YW Manual 3 Lesson 36 lesson is about Marriage Standards. 
This is the suggested quote from the lesson to be made into a poster. You can download it here. You will get the best printing result if you download the file to your computer, then open again in Adobe Acrobat.
I found another fun visual aid from the “Why” book to go along with this lesson. You can do this to help support the “being equally yoked in marriage” section. Talk about a three-legged race, how partners in the race need to be in step, neither one moving too fast or too slow in order to get to the finish line. Eternal marriage requires both partners moving together in the same direction to get to our desired destination in the Celestial Kingdom. You can read more details about it here on the Why website.
You could then bring a bandanna, strip of cloth or rope to have a couple girls demonstrate (carefully!), and also incorporate whatever item you choose into a handout.