There is no foolproof way to know if a tiler is good or not, but there are definitely some things you can do to make sure you're hiring the best tiler for the job. First, ask around for recommendations. Friends and family members are a great source of referrals for reliable tilers. Second, look for reviews online. There are many websites where you can find reviews of businesses, and it's a good idea to check out reviews of tilers before hiring one. Finally, schedule an interview with the tiler and ask him/her questions about their experience and qualifications. This will help you get a sense of whether or not the tiler is right for your project.
Hire a tiler! Seriously, this is not a question that can be answered without more information. Every tiler is different, and every job is different. You'll need to ask the tiler for references and look at their past work to get an idea of their quality. You may also want to ask them questions about their process and what they'll do to make sure your tiles look great when they're done. Good luck!