There are lots of people who say that they're UI/UX designers today. Almost anyone can start a website that's about UI or UX design and claim that they know the field and they know the business. It's your job to figure out who really has the skills and who doesn't, which isn't as difficult as it might sound initially. You just have to take the right steps and keep certain things in mind during the evaluation process.
Read Reviews and Look for Positivity and Negativity
You'll probably read customer reviews before you buy a blender these days. If you're hiring a UI or UX designer, you should definitely try to find any customer feedback that you can find on them. Even if they have just been mentioned on a web forum at one point, it should still be possible to find some outside information on them and their past activities. If there isn't, that's already a warning sign. It might mean that they're just talented but inexperienced, but you probably don't want to be the company that takes a chance on them, even if someone has to do it.
If there's lots of information on a given UI or UX designer and some of it is negative but most of it is positive and there's some neutral information, you're probably dealing with a great designer. Great designers attract a lot of feedback, and they tend to attract a range of feedback. Design is subjective, so of course, some people are going to be dissatisfied. As long as most people aren't dissatisfied, you're probably dealing with someone you would want to hire.
Similarly, the best UI/UX design portfolios will show off the errors that designers have made in the past and how they went about repairing those errors. UX design is always work-in-progress, and the talented designers are the ones who know how to correct mistakes. The ones who don't make mistakes are liars.
It is true that these days, it can be difficult to confirm whether a review is honest or not. Writing falsely positive reviews or getting generically reviews written is very easy today. Some savvy people will even get falsely negative reviews written today to create the illusion of honesty. Fake review writing is a business now. However, the reviews that you'll find about a particular designer or design company can still be valuable sources of information, even if they can't reliably tell you everything.
It's important to note that some of the content of UI/UX design portfolios may not be public as a result of the Non-Disclosure Agreements that they might have signed with some of their previous clients. Designers who make this clear have probably worked with some high-end clients in the past, and it isn't necessarily a warning sign of anything. However, they should still have some material that is public and that demonstrates their skills.
Dismiss Certain Types of Experience
This is a society of resume padding. Resume padding in this technical age has gotten even worse in some respects, because there are plenty of different ways to feign technical experience thanks to all the shortcuts out there. Lots of UI/UX designers have created their own apps. Lots of people who are not UI/UX designers and don't have any of the other necessary skills have also done the same thing, and it's important not to assume that just because someone has products in Google Play, you're going to be able to get good products out of them.
Lots of the most experienced UI/UX designers are going to have substantial web presences. They'll have blogs, apps, websites, and probably a selection of web videos where they show off all of their knowledge and explain their skills. It's a good sign if they have all of that. However, these assets are only the proverbial icing on the cake, and the impostors try to make them the cake.
Get a Sense Of Their Exact Abilities in UX Design
Lots of people can claim to know about UX design, but UX design is ultimately extremely broad. If you're outsourcing design to a web design company, you need to know if they can handle your exact requirements, and that means you need to know what they can do exactly.
You should get a sense of how they are at the motion, interaction, and visual parts of the UX design. Of course, user research, information architecture, and directing projects are also very important abilities that you should try to pay attention to when you're looking at the portfolio and the experience of a UI/UX designer.
Similarly, creating wireframes isn't impressive enough to show that someone has the skills to be a good UI/UX designer for you, and it's the sort of qualification that people tend to rattle off when they're exaggerating their design skills.
However, it should also be noted that the interpersonal skills of a UI/UX designer can be nearly as important as their technical skills. No one completes designs like these completely independently. People who know Java, Apex, and all about usability research but don't know how to work with other members of their groups aren't going to be effective hires. The importance of social interaction never goes away, regardless of the context.
Get a Sense of the Designer's Mindset
They say that writers are people who can't help but write and that this is an essential part of their mindset. They say that scientists enjoy being proven wrong, because they care more about what's true than what they want to be true. If you're looking for a writer or a scientist, you need people who think like that. If you're looking for a UI or UX designer, you need to find someone who knows that design work is never finished.
All design projects are perpetual works in progress. The new designs will get rested by everyone from clients to users. If there's a problem, then the designers need to fix it. If something needs to be updated, the designers need to do the updating. Designers who just want to walk away from a project upon its supposed completion just aren't going to be reliable in the general scheme of things. The designers who think this way will usually reveal themselves when they're interviewed.
UI/UX designers who think of themselves as artists and not artistic engineers are also probably bad news. They're not going to have enough of the specific knowledge that UI/UX design requires, and they're probably not going to be good enough at the marketing or management side of things. Design like this forms an important intersection between art and information technology, and people can't be too far on either end of the spectrum.
UI/UX designers who see themselves as artists will make their portfolios look beautiful, but they won't emphasize the problems that they are capable of fixing. If you're looking at a UI/UX design portfolio, it is important to avoid getting distracted by a portfolio that's nice to look at, which is a common trick. The portfolio will tell you all about the mindset of a UI/UX designer, and the mindset of the designer will usually help you anticipate the quality of their portfolios.