GMAT Strategy

I'm going through the OG 12 Quant review, alternating between the review text and review questions. I noticed that about half of the questions that I get wrong, I don't get wrong because I don't understand the concepts behind them, but because I'm answering the wrong question (like solving for x instead of y) or making a careless mistake (like adding when I should subtract). So is there a recommended strategy to minimize errors like this? For example, should I dedicate a ful 20 seconds to understanding each question thoroughly before answering? Will practice be enough to make me more cautious?