Remember RUCSAC.
R - Read the question - what does it really say, if you can't read a word or it doesn’t make sense ask an adult to read it to you.
U - Understand the question - what is it asking for, visualise what is happening, underline the key information, draw a diagram if necessary. Consider/ estimate what a sensible answer might be.
C - Choose the calculation - the clue will be in the language - you can find lists online of which operations key words would indicate, but context is key. Write the calculation in a mixture of words and symbols.
In a two-step operation, one piece of information in the calculation is missing and has to be derived as the first step. Put the calculation to obtain the missing information in a box beside the main calculation. Dividing the page in half and putting the second-step calculation on the right hand side, and then the first step calculation in a box on the left hand side can make things more organised.
S - Solve the calculation(s). Write it down, even if solved mentally. Always show the working out as often there are method marks. Start each part of the calculation on a new line so each line makes mathematical sense (what is each side of the = should be equal).
A - Answer the question. Sometimes this involves rounding up or down, depending on the context e.g. if the solution to the calculation is a fraction but the question is “How many children...” the answer needs adjusting to the next whole number above or below. Similarly, a money or measurement question may need converting into the requested units.
C - Check the answer. Is it reasonable? e.g. if your answer suggests a cat weighs 500kg or 500g, it's likely to be wrong. If you multiplied by 5 then the answer should end in 0 or 5. Have you put the right units in?
Sometimes, having a similar question with different numbers, and the answer, and working out how to reach the answer is a useful strategy.