Currently, there are no objective certifications or ratings which can help you find the best Kilimanjaro guides. We are hoping to change that eventually and create an industry standard. However, there are ways that you can increase your chances of finding an experienced and well-trained guide.
Firstly, you should book with a responsible tour operator. They tend to have the best guides, because they are better paid, trained properly and given the resources they need to navigate the mountain.