There are some general rules that every style guide should have:

• Include enough to build a website from it - with the styles, examples and color palettes you provide, one should be able to create a complete website or mockup.
• The style guide must have examples - I've saw several style guides with great explanation and clear purpose, but the lack sample codes made them unusable. Add consumer ready code and your colleagues will love you...forever!
• Make sure the style guide is easy to understand - a newcomer or an intern should be comfortable using and understanding the style guide.
• Organize your style guide and stick to it - try to keep the style guide organized and clear.

Here is a wonderful website with all kind of resources about style guides - styleguides.io

@Kleo said everything, this project may help you! (:

Basically what @Kleo said, but I will add: make it simple for the front-end for him/her to take elements, colors and objects from your template or your style guide. And for the love of god give the images to him/her outside Photoshop, Illustrator, Sketch, Experience Design, etc and at full resolution and optimized for web, you don't know how much time the frond-end developer will have to spent to searching the images, getting the exact color from your file exporting and cutting the elements, etc etc. Specially if you have a deadline so close think about him/her too. I've seen our designer relaxing and chatting with everyone in the office while I'm there suffering dealing with his template and asking him for the images at full resolution.