1. Make Practice a Priority
If diagrammatic reasoning is new to you, familiarising yourself with the concept is key. In taking plenty of practice tests, you'll learn the most effective way to approach each question, lessen any test anxieties, and build confidence in your problem-solving abilities.
2. Don't Attempt to Work Backwards
Focus on understanding the logic, rather than trying to fit possible answers into the puzzle. Working backwards is time-consuming, and since the multiple-choice options are often similar, it's easy to slip up if you've not fully explored the governing rules.
3. Manage Your Time
If your test allows you to use your time freely, look at how long you've got against the number of questions, and split your time accordingly. Remember, questions may get progressively harder, so you may want to leave more time towards the end. Taking practice tests under timed conditions will help with your time management.
4. Learn to Spot Distractors
In any given question, there may be elements present that bear no relevance to the underlying logic. These are known as distractors, and are there to add complexity. You need to learn to quickly identify what is pertinent to the problem, and what has been included to distract you.
5. Take an Educated Guess
Most diagrammatic reasoning tests do not apply negative marking, so you won't be penalised for an incorrect answer. Double check that this is the case, and if it is, hedge your bets by taking an educated guess on any questions you're unsure of.