Hi Christine,
Thank you for posing this question. I find it to be excellent practice, and I thoroughly enjoy it! Currently, I don’t hold a marketing role, so this serves as pretend practice for me 
Regarding the five fundamental steps for integrating behavioral marketing and customer segmentation, the most challenging aspect for me [at the moment] would be defining the interactions you want to track and analyzing and reporting how people are behaving on your website. It’s challenging because nearly every action a customer takes on a website is essential. The micro-decisions carry significant weight.
-Alanna