Know Your Character Sheet
Take the time between to learn where things are on character sheets. As long as you are using the same format character sheet, no matter which character of yours you are playing, you should know where to look when the DM asks for AC, initiative, your scores, your modifiers, your attack rolls and damage, etc. You don’t by any stretch of the imagination need to have the contents of the sheets memorized, but you should take the time to learn where to look. Knowing where to quickly find information is just as important if not more so than knowing the information itself. I’ve covered these parts in a separate post; link is below.
Read Chapter 9: Combat, in the Player’s Handbook
This section of the rulebook is applicable to all players and the DM. This section of the book covers most of the generic elements that you are going to be doing in combat, or at least the general mechanics of them. Actions, bonus actions, movements, reactions, etc. are covered here. Information relating to the specifics of spellcasting are in Chapter 10.
While I’m on the subject, turn to page 195 in your Player’s Handbook. Please. Look in the lower left corner, and read the section on Opportunity Attacks. Come back to my blog post when you are finished.
Done? Good. Now read it again, please. I don’t know how many times I’ve seen this one misused or misquoted. We all tend to remember simplified versions of rules as they were first explained to us. I’ve seen a lot of people (myself included) who had a rule told to them at the table, explained as it pertained to the specific situation at hand, and then misapply that to other situations because they hadn’t ever read the actual rule themselves.
Spellcasters, read Chapter 10: Spellcasting, in the Player’s Handbook
Spellcasters, you really need to read this section once. It explains how magic works. Components required, casting times, preparing spells, rituals, etc. It’s not that long of a chapter, and you don’t have to memorize it, but if you don’t read it you’re going to keep butting heads with your DM as you attempt to do things that aren’t legal in D&D.
Now, turn to page 202. In about the middle of the page, there is a section labelled Casting Time. Please read this section now. Please read the Bonus Action subsection again. This one trips a lot of us up. It seems that everytime I or someone else at the table tries to quote it, we get it wrong in mechanically significant ways.
Read the Adventure League Player’s Guide
Each season of D&D Adventurer’s League they update the rules that exist solely for Adventurer’s League. The main rules for players are currently 4 pages long. Please read them before playing. This cover the basics for Adventurers League. If it doesn’t answer your questions, the FAQ and the Dungeonmaster’s Guide to Adventurers League are also available for free online. Feel free to ask questions, but you are expected to at least read the player’s guide at some point. I recommend printing it out and carrying a copy with you for reference, since it’s so short, but be aware that it will change periodically. They can be found here:
Tab the chapters of your Player’s Handbook
Few things are more frustrating than having to stop a session for a few minutes to look up a bit of information. I find that putting easy to use, labelled tabs on my player’s handbook greatly speeds up my ability to find information. I put tabs on each chapter on the side, and occasionally I’ll put temporary ones at the top of the rulebook for things that I use frequently, such as the wizard class section when I’m playing a wizard. Tabbing the rulebook isn’t a requirement, and is usually considered above and beyond the normal prep expected, but being able to quickly find information can be almost as good as already knowing the answer. We can’t all have photographic memory. I’ve found this so useful that I’ve tabbed ALL my rulebooks this way (YMMV on the other rulebooks, they aren’t all as neatly delineated as the player’s handbook).