The SHL test covers three things: verbal reasoning, numerical reasoning, and sometimes a situational judgement test.
Verbal reasoning is just reading a passage and deciding if a statement is true, false, or unclear. The only rule: use what is written, nothing else.
Numerical reasoning is basic maths with tables and charts. The maths is easy. Speed is the real test.
Situational judgement is about picking the most professional, calm, client-aware response. There is usually a clear right answer.
Just practice a few timed SHL samples before you sit it. Not to learn tricks, just to get comfortable with the pace. That is usually enough.
Good luck.