It is important to research all products available on the market and to look into materials, formats, patterns, designs and colours. Colour is generally a good starting point as it sets the tone and feel of a space. Neutrals have always been favoured over brighter hues simply because they suit most colour palettes and styles. Out of all neutrals grey is generally the colour that creates the most response to the eye and it has become quite a popular choice for both interiors and gardens. Grey is also popular with designers and architects as it works well with most schemes and is effective with most architectural styles and decors.
If it's a more luxurious look you are after then marble and granite should definitely be at the top of your list. It's important to make sure that the material selected suits the application and that it can be sealed for durability if needed. Shopping around clarifies doubts and makes decisions easier so be sure you take your time and consider all options. Formats and patterns are also key to a design, generally bolder patterns are used in commercial applications (cafes and hotels) and can also make a striking feature in a residential project. Texture is also a great way to create visual interest and add tactility to a design.
If you are shopping around for tiles, putting together a mood board will help you get the project started, collect some colour cards in the hue that you favour and some images from magazines (or online on pinterest and houzz), it will be useful when questions arise later. If you have any doubts and need help with editing or just feel overwhelmed by the whole process, it might be a good idea to hire an interior designer or decorator, it'll make it a far less stressful experience and (probably) a much quicker one. Whichever route you may decide to take just remember to have fun and enjoy the ride:)