1. Nothing can replace Brand Awareness in a highly competitive niche.
When you are promoting services or products in higly competitive industries (such as beauty, fashion, travel etc.), brand awareness will outweigh product quality and even price.
2. Images convert better than videos (the exception is gaming industry).
Whether it`s single image or carousel ads, photos will always generate better results than videos when it comes to conversion / sales campaigns.
3. Reviews are key when it comes to ecommerce.
If the brand is known, the price is right, but the reviews are missing or negative, the sale won`t happen. So put in the effort to get good reviews and make sure they are visible on the product page.
4. Experience doesn`t replace testing.
Even if you have extensive experience for a certain product / service / industry, that doesn`t mean you can skip the testing phase when first setting up campaigns for a new business.
5. The client shouldn`t be a spectator.
It`s not like in the design industry. The client needs to get involved in creating a buyer persona, providing feedback and making changes when changes are necessary.
What are your tips for setting up effective Facebook Ads Campaigns?
Marele Diminutiv 
Excellent insights, Vlad. By now, I am testing same campaign, but with two different creative ads: Images as carousel and Video (Motion Design) for an ecommerce client.
Lets see which one is more envolved. Cheers from Brazil.