Before you can begin playing D&D, you need to create or select a character as your adventurer. Characters are a combination of game statistics, role playing hooks, and imagination. In D&D a character's class and race drives many of the interactions and decisions made to resolve encounters and combat. The following are resources and tips for character creation.
Guidelines for Character Creation
Player's Handbook by D&D Basic Rules
Character Sheets
D&D Beyond is website for all things D&D. It is created and maintained by Wizards of the Coast. By registering for a free accounts players can create up to 6 characters, create and participate in campaigns, and create homebrew spells, monsters and magic items. Subscription accounts allow for unlimited character creation and other benefits, especially for DMs and groups.
Geek & Sundry, created by Felicia Day, is a site devoted to RPGs, LARPing and gaming. The website includes a Beginner's Guide to D&D Character Building.
Handbooker Helper is a YouTube series by Critical Role exploring different aspects of playing Dungeons & Dragons. The series includes several episodes on building characters for beginners.
Roll20 provides digital support for tabletop gaming along with resources to design and play RPG games. The Roll20 wiki provides tools for creating characters in a virtual environment for either online or tabletop play.