1) Not taking care of his tools and being messy. An easy, yet not bullet proof way to tell your contractor is not as professional as you think, is if he does not keep his tools well. This means not keeping them in good shape, and also not putting them away or storing them properly. Take a peek while he's packing up for the day or unloading in the morning. If his van is messy, dirty and full of unorganized tools, that's not a good sign. Sure some messy people can be good but typically professionals will keep their tools in working order and organized as well.
2) He wants to work at a daily rate, not for a decided upon price. This is a huge tip-off that the person installing your tile is not honest. Any professional should be able to give you a price for the job at hand and stick to it. Allowing someone to work at a daily rate is just asking to have a job take 2-3 times as long and end up being 2-3 times as expensive.
3) He doesn't clean up the worksite. This is another bad sign. If a contractor does not respect the homeowner enough to keep the area clean and free of dangerous debris, that does not show much for his integrity. Any tile pro worth his salt will make sure all tools are neatly put away, rubbish is collected, and any holes are filled in before leaving for the day. They will only leave after making sure the site is clean, safe, and secure.
Keep these 3 simple warning signs in mind when hiring a contractor to install your tiles. It's way better to play it safe and go with someone who does not exhibit any of these bad habits. That's because all three of these things usually go along with laziness, dishonesty, and poor workmanship. Take your time, do your research, and don't be afraid to fire or not hire anyone who does any or all of these three things. Remember when dealing with tiles it's always cheaper to do it right the first time.