I would say that if it is a recipe you are unfamiliar with than yes, it is very important. For example, let's say you are making yeast rolls. The recipe ingredients call for 2 cups of flour which you have. If you don't read through the whole recipe though, you might not know that you need more flour when it comes time to knead the dough. Also, some recipes will claim to have a 30 minute prep time and a 20 minute cook time, but they don't tell you about the 24-48 hours of down time you need for the dough to rise unless you actually read the recipe. For recipes like that I would definitely give it a read through first.
On the other hand let's say you are making something like grilled chicken. While you might need some extra time to marinate it, you are probably not going to run into any surprises while as far as cooking time or ingredients go. In that case I would say it is fine to dive right in!