Step number 2 - Prime the floor !
Not with watered down PVA but with the correct primer for the job.
Some adhesives are now 'self priming' but I always still think this should be done. Especially in an area that has had dust or on new substrates.
This floor had some levelling compound put down ( not by me, which is why it's not 100%) and it will want to draw the moisture from the adhesive. This primer will help the adhesive cure in it's natural way and achieve a better bond.
We're going to tile this small kitchen floor over the next day or so and share the process.
We'd always advise getting the professionals in but if you are a keen DIYer this should help. Also so you have an idea of what the people you hire should be doing, should you be concerned you've hired the wrong people for the job.
Number 1 - Clean the floor. Easy peasy with an heavy duty vac like this one. We want the floor to be completely free of dust before we do anything else. Even sweeping up doesn't lift it all so a Hugh power vac (Hoover if you prefer) is the best thing for the job.