Lots of great resources and information here on the forum so don't be afraid to use the search feature and ask questions.
I second what @squeegeethree and @Grantmesteven said.
Think about what you want your beer to be. The style guides can be very helpful to point you at recipes so you can research the ingredients and understand what they can do for your beer. I tend to think of the malts as the backbone and the hops like the icing on the cake. Different yeasts can add or detract from your beer so make sure you read about and understand what your yeast is bringing to the party. Keep things balanced. The BU:GU ratio was a game changer for me. Don't be afraid to exbeeriment and don't sweat perceived mistakes. It'll probably still be beer.
Mistakes I've made include: going wild with IBUs, not understanding my malts and their effect on the finished product, winging it, using too many varieties of hops so it's a muddled mess, and many more.
Good luck and happy brewing!