The first game of D&DB I ever played (which goes without saying, my first game of D&D ever) was as Dungeon Master (DM). I had read the rules cover-to-cover (the booklet wasn't that big back then) and was going to run a short adventure into an abandoned keep. I found a few of my junior high school friends and gathered around the table to play on a warm summer afternoon. With weapons in hand, the characters set off in search of Adventure.
Things were sailing along smoothly (for less than 5 minutes) until the party encountered its first obstacle: skeletons. Skeletons were labeled as first level monsters and the party was full of first level characters; a perfect match. The problems didn't start until the characters started rolling dice to hit the skeleton. They rolled and missed. The skeletons would roll and miss. The party would roll and miss and then the skeletons would roll and miss. This went on for several minutes before one of my friends asked how this was supposed to be fun. Something was amiss.
I checked back through the rules on combat and re-read them. I soon discovered my fatal mistake. When determining the number needed to hit the skeletons I took it as literally the number needed to hit; the party had to roll that number and nothing else would do. Well, red faced, I quickly discovered my misinterpretation: the phrase "...or higher..." seemed to slip my memory when it was time to play. Combat went much smoother after that.
This small detail goes to show how drastically a misunderstanding of a rule can impact the play of a game. Some games are complex and require an intimate knowledge of the rules in order to run smoothly. Some games are simple but open to interpretation. Both present challenges.
When handling a game with a very large rule set it is often best to take it in chunks. Focus on the rules that will be used first. In the introductory chapter of Mouse Guard, Luke Crane outlines the four chapters of the book that should be read first in the section entitled 'Getting Started'. Character creation is not one of the chapters listed. In fact, character creation is one of the last chapters in the book. IMO, Luke is saying, "Wait! Before you even think about creating your character, play the sample missions with the sample characters to see how the spokes fit in the wheel!"
In D&D I look at rules on an encounter-by-encounter basis. Whether reading a prepared encounter or designing one from scratch, I ask myself this question: "What do I need to know in order to run this encounter." I open the rule book to the index and start boning up on rules that will be utilized. Next I look at the characters in the party and see what they could possibly use to resolve this encounter: racial and class traits, feats, type of combat favored, spells.
The last one deserves added attention. It is prudent to read over the spells that both the players and NPCs have access to. I did this not very long ago where I was operating from what I thought the spell did as opposed to what it actually did (just goes to show, it doesn't matter how old you are, there is always room for improvement). Bottom line - read over the spells often to be sure you are on track. Don't worry about the spells that the characters can't cast yet, focus on the ones they have access to.
For games with less structure a healthy dose of interpretation is required to make things move along smoothly. To help prevent misunderstandings I recommend creating a social contract to outline the expected behavior and guidelines for handling disputes. This can be a simple as "if we get stuck we'll wing it" or "we'll roll for the outcome and discuss it after the session". Play of a wide variety of games helps to provide players with a resource of numerous options - "we did it this way in Shadowrun, so let's do the same thing here." For groups that have played together for a long time the social contract is more implied than explicit, but it never hurts to discuss the contract to keep it fresh in your mind.
It should be noted that while the preceeding paragraphs were from a DM point of view, the same holds equally true for players. Know the rules that apply to your character. If you play a cleric, know and understand the rules for turning undead. If you play a spell caster, know your spells and all the rules that apply to spell casting (range, spell components, recovery, saving throws). Don't put everything on the DM's shoulders, step up and help lighten the load.
It wasn't long before I realized that knowing the rules applied to pretty much anything you came across in life. We spend a good portion of the first 18 years of our lives 'learning the ropes' before we are considered an adult. Heck, I'm still trying to keep it all straight. Rules give structure and order and should (hopefully) be equitable to all parties involved. Whether it is office culture or computer programming, take the time to learn the rules. If there is a lot of ground to cover, learn what you need to get the job done. If the rules are a little nebulous, fall back on your past experiences and do your best. We're still gonna make mistakes, but hopefully they are mistakes we can learn from.
Follow Your Bliss,