Starting at the Very Beginning
There are so many things for table top gaming that it can be hard for brand new players to know where to start. This article has some of the things that DM Wolfsfox recommends and follows to make gaming work smoother. What I have typed here is my opinion and can be followed at your own discretion. Here are the top 5 things I recommend for a smooth game.
Start New Players at Level One
The best way to get a feeling for a character's personality, playstyle, class, etc. is by creating your character and starting at level one. For new players Level 1 is a must in order to learn rules and class features with out giving yourself an overwhelming amount of things to work with. When you start at level one then the lower levels of 3 and 5 feel more earned instead of starting at lvl 3 or 5. Instead of rolling for personalities or backstories players can explore what feels more natural to them through the first levels of play. Level one lets you explore why your character got called to adventure. If your adventure/module starts with something happening that called for action by the pc's perhaps this is the first time that your character has felt the need to explore past their town walls. There are many things to play with and explore with a character starting with 0 xp. A blank slate is always the most fun to experiment with.
Once players have some experience or feel comfortable then you can consider starting at level 3 or above. You can also consider then using campaigns/dungeon crawls that start at higher levels such as The Hidden Shrine of Tamoachan that starts at lvl 5 or Dead in Thay at 9th level.
Have a Players Handbook
I recommend that players read the Players Handbook at least once from cover to cover. All of the main core information is in that book and it is important to have at minimum a basic understanding of the game. You don't have to have everything memorized or know every single rule written but it is important to have basic understanding or have the Players Handbook available for reference as needed.
As a DM I also value the Players Handbook over the Dungeon Masters Guide. There is so much information that players and DM's alike need to know form the Players Handbook. I don't believe that you need to know all of the rules or be an expert to start playing D&D 5E. Many of the starter modules are new player friendly and helps players get their bearing with the rules and how to play the game.
Pick Your First Module Wisely
First impressions are important. You don't want your first campaign that you play in to be the reason to leave ttrpgs forever (example: no starting with Tomb of Horror).
DM Wolfsfox recommends:
The Lost Mines of Phandelver
Dragon of Icespire Peak
Sunless Citadel (more of a classic dungeon crawl)
Though randomly generated characters can be fun, if you are making a character to play in a long term campaign I recommend doing a little research before going into character creation. There are a lot of different places that have recommendations and sources about the different classes and character optimizations that other players have found work well/don't work well. Reddit, rpgbot, the gamer are just a few of the many different places out there you can find information on. What I do is look at a few different articles and make some comparisons between what I read. I am not a big Min/Maxer but I do try to make sure that I do enough research to avoid things that are not helpful or broken.
Session Zero Magic
As a DM I always recommend having a session zero before you start a game. Whether the group is starting a new campaign or bringing a new player into an existing group there is so much to be gained in a few hours. Not only does this make sure that you have a character built to your DM’s expectation it also is a chance to talk to the dm and other players to make sure that everyone has similar goals in the game. It's a time to discuss table rules, expectations and homebrew. This is where a dm can give an introduction to the module or world. It's important for players to work together so having time to build characters together helps make sure all bases are covered. As a group it's important to talk about campaign preferences in regards to role play, combat, and other game components. You want to make sure you are not the only rp player in a group of murder hobos. A session zero also works as a time to get to know others at your table or catch up with friends.