I always said that to avoid mistakes and a wrong answer, you need to be organized. That is, when working a math word problem, try to space out the work area on the paper. An easy way to this is to place a line on the right side of the paper and write formulas, conversion factors, or any other data that you might need. In this way, you have all that you need to work on the problem without thinking about 'where's that formula?' or 'what was that conversion factor?' Sure some people are really good at memorization but I believe you need to focus on understanding concepts. Once you fully understand concepts, that's is the true value of learning.