A subreddit name is permanent
You can change a subreddit's description, banner, icon and rules whenever you like, but not its name. The r/ name is fixed when the community is created, and it is how people find, type and link to it.
That makes the name worth a few rounds of ideas. Describe the community in the form, generate, and look for a name people would type into search when they need your community.
Spelling within Reddit's format
Subreddit names can't contain spaces or hyphens, only letters, numbers and underscores, from 3 to 21 characters. Capital letters help readability ("r/HomeBrewHelp" rather than "r/homebrewhelp"), and an underscore can separate words when capitals would be unclear.
If the name you want is taken, look at that community first. If it is active, joining it may serve your members better than starting a rival. If it is empty, choose a more specific name, for example by adding a place or a skill level.
Setting up the community
Once the name is set, finish the community so it looks cared for: a banner at 1920 x 384 pixels, an icon at 256 x 256, a short description and a few rules. People decide whether to join in a few seconds.
Post a few useful threads before you invite anyone, so new members land on conversations instead of an empty page.