My DO: Use Google Ads Scripts (sorry, no surprise here I guess). Google Ads scripts are free, make your mouth curl into a pleasant awe-struck smile every time you run one, and do not require any coding skills to get started.
My DON’T: Run Display and Search in the same campaign. You’d be surprised how many SMB advertisers have this enabled.
Please share yours, I read every one.
– Nils
PS: Bonus -> don’t forget to check your ad group level “Targeting expansion” setting in Display when submitting campaigns via Editor. I’ve seen weird changes in my settings because of doing this.