Choose the relationship first
Ask whether the next idea adds information, contrasts with it, explains a cause, or shows a result. Then choose a connector if one is needed: 'also', 'however', 'because', or 'therefore'. A connector cannot repair a connection that does not make sense.
Carry familiar information forward
A phrase such as 'this extra hour' can refer back to a later closing time. Give pronouns a clear noun to refer to. Repeating a key term is often clearer than replacing it with a distant synonym.
Use sentence length deliberately
Join closely related ideas when the connection helps: 'Because the room is small, we can try four desks first.' Keep a short sentence for a key point. When joining two complete sentences with 'however', use a full stop or a semicolon before it, not just a comma.
See it in practice
Starting point
The new timetable would help students. However, students could borrow books after clubs. It costs money, it needs planning.
Using this skill
The new timetable would help students borrow books after clubs. This extra hour would give them time to browse. However, staffing would cost money, so the school could begin with a four-week trial.
'This extra hour' carries the idea forward. 'However' introduces a real drawback, and 'so' connects that drawback to a practical response.