Dorian's Start Guide

Most of D&D seems much easier when you're playing. I reckon there are only a couple of things that need attention before the first session.

First, check out the introduction to the The Player's Handbook (PHB). That'll give the basic idea of how a game goes and what's involved.

Second, you want to create a character. Chapters 1-5 of the PHB will guide you through that. I personally reckon, pick a race and a class that appeals to you as a starting point, and everything else sort of comes together. You don't want to worry about getting every little detail right. You'll understand better when you start playing and you can always change things then. One place that's quite nice to check out is the RPGBOT Character Optimisations. There, you can see a bit of logic behind character planning. Though of course, many people prefer to roll dice to determine their characters randomly as described in the PHB. The D&D Beyond site has a character builder, which can be helpful as a click-through step-by-step builder. It makes the technical side of character creation much easier, but of course you'll understand less how your stats and whatnot come together as much of that is automated. Two final points. Consider your party, when you're choosing a class. It's usually preferable that every party has a healing-type character (Cleric, Druid, Paladin), or else you're much more liable to die (and yes---characters can die, which is pretty irreversable at early levels). Lastly, your backstory is mostly for your role-playing delight, but it's often fun if there are some hooks or blank spaces in there that the game master can use to integrate your story into the game. Missing sibling? Let the game master decide who was responsible and where they might end up---you might see them again on your adventures. A quest for redemption? Leave it open what redemption might look like, so the game master can weave the right circumstances into things. You get the idea.

Third, speaking of, check in with your game master. They'll be able to tell you if what you've done looks good, or if you should change stuff. Also, they might need to correct bits and pieces for you, here and there. Better to get that sorted before the first session. Lastly, it's particularly good to check your backstory with the game master. Firstly, they'll want to know what it is so they can try and build it into the story. Secondly, they might help you adjust it so it sets up more sensible for the start of the campaign (it's no good your character living somewhere the campaign isn't happening). Sometimes, the game master will build this opportunity in with a 'Session Zero', but if they don't just reach out.

Mostly, though, I want to emphasise, don't worry about getting it all right. Put something together, and then if the first session makes you realise you need to sharpen things up, talk to the game master and change things. Most of the concepts are going to be a bit alien regardless of how much reading you do before hand (if you're a dummy like me). Get to playing and they'll make much more sense. In the mean time, I'll leave any particularly useful resources I find here, and there's plenty more online.