What are the some best practices to follow while transitioning from waterfall to agile?

Chitranshu -

Depends on the project's context and what you mean by "middle". If baselines for scope, cost & time have already been committed, then you may start delivering in an incremental, iterative manner, but I wouldn't necessarily term this "agile" as the degree of openness to change is likely to be low.

A "Water-Scrum" pattern might fit this situation. If you have requirements on external validation which cannot be addressed within short delivery windows, then you could have "Water-Scrum-Fall".

Kiron