Most cloud migrations do not fail because of technology. They fail because of a missing initial inventory, unrealistic timelines and no documented rollback plan.
The first step is an honest inventory: what systems exist, who uses them, how often and what would happen if they were down for four hours. Without that, any migration plan is fiction.
The '6 R' framework (rehost, replatform, refactor, repurchase, retire, retain) remains the practical reference. For most SMEs, 70% of systems go to rehost and 20% to retire. The remaining 10% is where the real work is.
The first cloud year almost always costs more than expected because you are paying for old and new infrastructure in parallel. Budgeting for a three to six month overlap is more honest than promising immediate savings.