Defining Problems & Competitive Analysis 

Before considering jumping into the actual design phase, finding out the problems that the team needs to solve can be critical. Being able to create competitive analysis and finding out the advantages/disadvantages when the product is going against other competitors on the market is also valuable to the team and stakeholders. As a result, an appropriate amount of research will be put into the pre-design stages, which will support the designers' point of view and help them to come up with a close estimate that the execution will cost. 

Collecting Requirements

A successful product is not only about targeting to meet the needs of customers and stakeholders, but also meeting the needs of team members from different departments. By looking into quantitative and qualitative research datas from other department members, the team will gain a better idea of user & market needs as well. Creating an affinity diagram can be very useful when it comes to managing requirements and prioritizing multiple tasks. By voting on particular tasks, the team will find out their exact priority and strengthen the team's hypothesis.

Personas

Create potential user and non-user stories for the products with different scenarios. This process helps the team determine the strategies, objectives, and target audience of the product. Personas also provide a precise path for the team when making important design decisions. 

Site Map, Wireframe & Rapid Prototype

Creating site maps, annotated wireframes, or rapid prototypes and discuss with the team, especially developers, to make sure the information architect is precisely done and accessibility is on point.

High-fidelity Prototype

Polished prototype with limited visual elements and interaction on the refined concept of the product. The tools I usually use are Axure and InVision, they are very easy to navigate and the interactions are there. It looks like the real deal, and that is very important when conducting a demonstration for developers or stakeholders.

Example: https://invis.io/TG61DECUQ