1, designer's company
Generally speaking, designers of formal companies are more reliable. As for how to tell whether a company is formal or not, it can be judged by asking the company about the completed orders, customer satisfaction and other information. If conditions permit, you can even refer to the door.
Step 2 communicate with designers
You can look at the designer's works, past design cases, and if you have the conditions, you can look at the site that the designer is responsible for. To judge whether he is a good designer.
Step 3 judge according to common sense
If a designer doesn't go to the site to measure the house and doesn't know some construction knowledge, please pass directly.
4. Design works
To find a trustworthy designer, you can collect designer works close to your favorite style. In direct contact, the designer will give you the answer to your question, from which you can judge whether the designer is suitable for you.
I hope it will be helpful to the subject.