>Watch some games of the system you’re playing.
>Play a module for new DMs first, you’ll need it. LMoP is good for DnD, but many games have starter sets, like FFG’s Star Wars System.
>be willing to improvise and come up with new ideas, PCs can be creative
>Use starter character so you can also learn their abilities
>A DM screen is helpful but not needed, if you can get one you should though
>Have multiple sets of dice, some for you and some for your players if they won’t be bringing their own
>Learn what’s going to happen, read and plan ahead for what might come but don’t over-prep, your players will always surprise you
>Take notes, it’s very helpful to look back on
>If you don’t know a rule, come up with something, note down what it is you don’t know and look it up afterwards
>Have fun, your first few sessions probably will be trash so don’t go to hard on yourself, you’ll get better
Good luck and have fun Anon