askchapo

Disclaimer: I have never used a pre written campaign. That being said, I find that creating a campaign is both easier than you might think and extremely fun and rewarding. As others have mentioned, the most important part is being able to improvise and yes and with your players. Just come up with the outline of a setting, (where are we, a few pertinent places/people), and an initial tension/excuse for why we need to start an adventure (maybe some potential antagonists and twists). You can develop more than that if you want to, but that's honestly all you need to get started. The world and its society doesn't need to be fully fleshed out because as your players explore it, it will become more fleshed out and hopefully come to life. You won't get it perfect the first time, but like any other skill you will develop it with practice and hopefully you'll have a great time with your friends doing it

You don't need to make a custom map, but here is a way to approach that if you want to. I like to start with a random real map, whether of a city, region or park etc. Ideally one your players won't be exceptionally familiar with. Very roughly and inaccurately sketch some key details onto a piece of paper (rivers, roads, coastlines). Maybe sketch a mirror image if your unconscious mind recreates the map too faithfully. Now turn that into an appropriate map for the campaign in question. Municipal Police head quarters? That's the evil castle of the main antagonist. Creek? More like mighty river. Golf course? Dragons lair. Or whatever feels appropriate to you. Pretty soon no one will be any the wiser.