A scheme of work sets the pace for an entire term, so it's worth getting right at the start rather than fixing it as you go.
Start from the syllabus, not the textbook. Textbooks are written for general use; your scheme should reflect the actual weighting and order of the TIE curriculum for your class.
Build in review weeks. Every scheme should have breathing room for topics that take longer than expected — because some always do.
Write objectives a student could self-check. "Understand fractions" is hard to verify. "Add and subtract fractions with different denominators" is not.
A good scheme of work is a plan you can hand to a substitute teacher and trust that the term stays on track.