Create a sitemap for your website. See example sitemap.

Sketch out wireframes for any unique pages on your website (i.e. for a portfolio website do the homepage, gallery page, project detail page, about page and contact us page). Once you have sketched out your idea and know where all your assets will be, create a high-level version of your wireframes using Illustrator (or another wireframing tool). Have these wireframes build on one of the grid layouts that you explored.

Site Map A:

Site Map B:

Sketch/ Wireframe 1-A

Sketch/ Wireframe 1-B

Sketch/ Wireframe 2-A

Sketch/ Wireframe 2-B