See the current state of the merge/rebase. Check git history, and the conflicting files.
Find the primary sources for each conflict. Understand deeply why each change was made, and what the original intent was. Read the commit messages, check the PRs, check original issues/tickets.
Resolve each hunk. Preserve both intents where possible. Where incompatible, pick the one matching the merge's stated goal and note the trade-off. Do not invent new behaviour. Always resolve; never --abort.
Discover the project's automated checks and run them — typically typecheck, then tests, then format. Fix anything the merge broke.
Finish the merge/rebase. Stage everything and commit. If rebasing, continue the rebase process until all commits are rebased.