Just like you have imprinted mathematical tables on your brain in your childhood, you make physics formulae too onto your brain. Don't let any formula miss out of your brain.
Always try to co-relate formula with its definition and units. They are inseparable. They are simply derived from one another. If you know formula that indicates that you know definition; you can derive units from it. Besides this generalize these with your daily life and natural laws and phenomena.
Always try to draw a line diagram depicting problems in your question paper with minute details visa vis quantities, dimensions, units, etc with consonance. Apply the most appropriate formula to solve the problem Cross check the answer to confide yourself.