Integrating TypeScript in Next.js Project

**Issue:**
I'm transitioning from JavaScript to TypeScript and want to integrate TypeScript into my Next.js project. What are the necessary steps, and how do I handle type definitions and interfaces effectively?

**Questions:**
1. How to set up TypeScript in a Next.js project?
2. What are the common challenges when transitioning to TypeScript?

**Additional Information:**
- Next.js version: X.X.X
- Current project structure: [insert details]

The issue does not identify files, tests, a project structure, or a concrete Next.js version. Start by reviewing the existing project and the relevant Next.js TypeScript setup guidance, then define the required setup, type-definition guidance, and migration challenges. Done should be a specific, project-informed guide rather than general unanswered questions.

Written by the indexing model from the issue text.